The issue is that I used a lot of Fedora, but it works surprisingly slow on my machine, but the support for developers' tools was awesome (never had problem with old versions). After that I tried ElementaryOS, which is beautiful and fast, but Ubuntu-based so every compiler I need to build from scratch (I'm testing new languages recently) so started thinking about something still nice and fast, but with recent stuff. Now i have a two days of continuous spare time and maybe will try Arch or Gentoo, which I know what's about, but not tried ever.

I'm a heavy Gentoo user and a weekend should be enough. Especially if you've compiled a kernel before (do this btw, don't use genkernel). As for speed, I doubt you'll really doubt you'll notice much. Memory usage and installation size is way more noticable. If you need a speed boost I suggest not using a Desktop Environment, but using a simple lightweight window environment (I use Awesome, some friends of mine use i3) in combination with xfce4 utilities, since they don't have a gigantic amount of dependencies and are very nice to use.

My dotfiles repository also contains my gentoo config files: https://github.com/JelteF/dotfiles/tree/master/etc/portage Don't copy paste all of it, but it might be nice to see what a config aquired over a couple of years looks like. And some stuff is just nice to have for a desktop/laptop that you regularly use.

I personally have not used Gentoo on the desktop, but I have friends & coworkers who have, and they have been generally happy.

Arch is awesome, I am not currently using it but have used it before.

Another possibility you could look into is Debian Testing. Debian has the reputation of including "old" packages for the purpose of stability, but the "testing" version of the OS is much more up-to-date, and if you need something even newer, and are feeling adventurous, you can install specific packages from debian-experimental.

The big thing is to make surr you have reasonably modern hardware. Installing on older systems could take a week or more for all the builds.

AMD FX-8350 and 8gb shall be enough, I suppose.