OBS lets you combine multiple sources easily including adding static and dynamic graphical overlays and is basically the what all of the streamers are using on all of the three platforms Linux, macOS and Windows these days, and aside from being able to stream live to Twitch etc it is also perfect for offline recording.
However, OBS is not a video editor, so if your use-case is to first record your screen and to then record the commentary afterwards rather than commenting while you are screenrecording then OBS is probably not what you want.
But Camtasia is both a recorder and editor and it seamlessly integrates the 2. The main pros of Camtasia is that it's super optimized for editing screencast style videos (tooltip overlays, text, zooms / pans, really REALLY nice animations on any objects by just dragging a few sliders, etc.). The editing part is where kdenlive is way behind IMO, but that's where you spend most of your time.
A vMix Call equivalent that transparently wires into the audio board would also be really nice, but I don't wanna get greedy.
Fair enough but audio is a completely different animal that can be tamed in a number of ways:
1. You can buy a hardware USB audio interface + mixer for ~$200-400ish total which can do compression, basic EQs, noise gate, has multiple inputs, etc. and now that becomes your final source of audio so you don't need to process it with software. It's just a mic from your computer's point of view.
2. OBS has VST plugin support, so you can directly use hundreds of free VSTs to do various effects in real time without needing to mess around with audio redirection. No hardware needed except for your mic.
3. You can use REAPER (free but you should register it, sort of like Sublime Text) which is a DAW. From here you can use various VSTs and then use Jack (or comparable software) to redirect REAPER's output as input to another app (such as OBS). This takes a bit of initial set up but technically would work with any app, not just OBS and this is what I used to do before going with #1 because I didn't want to run all of these apps every time I wanted to start recording.
In the end, you can get fantastic sounding audio with any of the above approaches and with #1 and #3 you can do it with any application where as with #2 you're limited to OBS only (which isn't a bad thing if you spend your time streaming and primarily recording with it anyways).
#1: that USB mixer acts as a mixer only for inputs that you can plug into that mixer. That may sound obvious. It becomes concretely painful when you have video inputs that also have sound attached. For HDMI captures, you might have an audio takeoff or you might use an HDMI extractor, which is...fine, such as it is, but suboptimal. If you use a professional stack--my video stack is SDI-based--this is completely inadequate. If you use NDI for video transmission over your network (and my stack has a switch in it, 24 gigabit and 2 10G SFP+, in order to take between six and ten NDI streams into the video mixer), you're boned; the only option that OBS offers, and it's a bad one, is to replace your cue/monitor output (assuming you have an extra audio out in your video mixer) with the NDI output. This means you can't practically mix NDI stream output that isn't currently on-screen because you only get one cue.
2. This isn't a solution because the OBS mixer is deficient. Modifying levels on the fly is impractical because they're just local UI widgets that lack the usual affordances for mouse-driven audio control. And this could be fixed with hardware but far as I am aware (this one might have changed since I last used it, OBS is now just an NDI slave for me), you can't connect a MIDI slider controller to the OBS mixer in the first place. You definitely can't send signals back to a MIDI controller to enable the use of motorized faders, which are one of those "I can't go back, I won't go back!" things now that I have them in my stack.
3. Similar problem to #1, only in software. Redirection turns into a virtual patch bay and you end up having to figure out how to run things back and forth. And the tooling on both ends is very rarely automatable, so you'd better hope you don't lose your setup.
The best option, and it also gets you screwed over because of UI affordances, is to use obs-asio with bassasio (and yeah, this means you're using Windows, but you probably should be anyway because #3 is better with a more serious DAW option, like Ableton Live, as your audio backend). You can pull every channel off your interface and expose them in OBS and you can squint at Qt sliders to your heart's content.
Personally, I use vMix instead and have good iPad-based applications that I don't have to write myself (like I said elsewhere in this thread, I wrote this[1] to control OBS remotely, it's not nearly as good as the stuff already available for vMix!) for both audio and video switching and I can, and do, wire up MIDI surfaces for physical controls (motorized faders, etc.).
Don't get me wrong: OBS is fine if your needs are small. I got pretty far with it. When your needs are no longer small, it turns into a Jenga stack of hacks. I hang out in the OBS Discord, I think the team is very talented, but the software has trouble scaling up even to my relatively modest needs compared to commercial solutions (vMix and NewTek VT being the best options in that space, though VT is gonna cost you both arms and both legs).
Had I infinite time, I would go take a chainsaw to the entire audio stack in OBS, but...I don't, and vMix already does it capital-R Right: multiple ASIO devices, first-class mixer inputs for everything from audio interfaces to cameras to NDI feeds to WebRTC calls (seriously, vMix Call is great). And it comes with a pervasive automation suite built around multiple kinds of input devices--DirectInput joysticks/controllers, keyboard shortcuts, MIDI signals (and not just notes, but faders etc.)--with signal-returns to enable stuff like motorized fader boards (which have gotten super cheap, too). Given all that, and the lack of having to do any of it myself? $700 is cheap. ;)
[1] - https://bit.ly/buymyapp
I'm coming at from a single person trying to record screencast videos in a controlled environment.
And OBS is in my standard kit. It's just fine as an NDI satellite. But also, for what you describe, there's a $60 1080p vMix package...and it's got most of the bells and whistles I described, too. Automation and control are easy to overlook until you don't have them!
I open a recording program (either Camtasia or OBS depending on what I'm doing), hit record and talk. Then I hit stop.
That's it. At this point my audio is leveled and comes out sounding good since all of the processing happens in hardware in real time. It's also sync'd with the video.
Editing is where kdenlive falls apart which is really what my reply was about.
Not a single person replied positively even though the post wasn't hostile in the slightest.
I want to see kdenlive overtake everything, but it's simply not there and given its progress over the years (I've been following pretty much every open source and closed source screencast oriented video editor for years) I don't see it ever getting there.
It's one of the reasons why I continue to stick with Windows. Kdenlive feels like it's 10 years behind Camtasia in terms of UI polish and being able to accomplish simple tasks like put a little tooltip overlay on the screen and make it look reasonable.
I think a lot of people who say kdenlive is good haven't tried Camtasia, or have created enough videos to really figure out kdenlive's shortcomings. I'm coming at this from the POV of creating 400 videos and have spent over 1,000 hours hardcore editing these videos.
I don't want to tear it down too much because it's one of the better screencast video editing tools on Linux but if your profession involves creating screencast videos, you're going to be majorly disappointed compared to Camtasia (or Screenflow). Enough to where you'll probably abort the idea of using Linux even if you're primarily a developer.
I wish I could throw money at the kdenlive devs and wake up tomorrow with a video editor that was as good as Camtasia.