No reason to get 5 pin DIN MIDI at this point; almost all devices offer USB MIDI and its as good as DIN MIDI in almost all scenarios.
[ EDIT: VCV Rack ] 2.0 will be out "soonish" which will offer an "official" VST (and if we're lucky, LV2 also) plugin, though at a price.
People's mileage will vary when it comes to the DAW. As the author of another (libre & open source) DAW, I get emails that vary from "Oh my god, I've used X and Y and Z and yours is so much easier to use and incredibly fast and reliable" to "how can you look at yourself in a mirror when you make such shit software". Reaper works for a bunch of people, but not for another bunch, as is the case for most DAWs.
DAWless setups are definitely a thing, and you need DIN MIDI to connect the keyboard directly to a sound module (USB can only be connected to a computer).
It is a $50-$100 extra investment to get a quality keyboard with DIN MIDI, but those quality keyboards come with better software and have a better build quality to them.
It’s a lot better to spend the extra money up front to get a keyboard with a DIN MIDI connection (e.g. an Arturia Keylab or Novation Launchkey) than to have something which will need a hacked together USB-to-DIN box (and I notice I haven’t seen any names of make and models of MIDI USB to DIN boxes which supposedly will always work) if they ever want to go DAWless.
• Get Reaper. It’s a mainstream DAW, is fully functional, a free download, and only $60 to register after 90 days.
• Valhalla Supermassive for reverb: https://valhalladsp.com/shop/reverb/valhalla-supermassive/
• The VST fork of VCVrack for a modular synth: https://github.com/bsp2/VeeSeeVSTRack#downloads
I would get a keyboard controller with full sized keys and a 5-pin DIN MIDI out for just over $200, but that can come later.
One thing to avoid is the rabbit hole of concentrating on what gear to buy over actually making music with the gear.