Compiling Firefox alone for speed may not grant a big performance boost. But all together, all the self-compiled things with ~1-2% performance boost each result in a really serious benefit all together. I also don't know if the guy you mentioned used all the flags he could. I know there are some flags you're recommended to stick with, but I would learn to take the maximum benefit of them, even if it is tedious to learn, bcuz mistakes in use flags cause trouble.

That was not plenty for me when I was into music production. Really limiting tbf. I want to take away some reserved RAM from the GPU, cuz I'm not gaming or mining crypto anyway. And I really want to use VMs.

Compilation is of course taking some time always, but I believe that with my current skill level and hardware it is not worth it yet.

I actually want a system that is fast, optimized and controlled. I wish it also wasn't asking for extensive maintenance, but it is not trivial to accomplish that with Gentoo or Arch. But still possible, with some trade-offs, but those are not very relevant for me. And yeah, I want a system that I know and understand, that doesn't keep any secrets from me. And I want powerful hardware, yeah.

Alpine is a good one, but it doesn't seem to suit for casual usage. I would use it, but as a server. That's what it was actually made for, I believe. Void is also great, but it has the problem of package availability. XBPS is not common, so one still runs into compiling things when using Void as a daily driver. However, I recently consider installing a custom Void flavor on my low-end netbook, which isn't snappy even with Debian Xfce. I'm going to install a minimal Void, and then add XLibre and LXQt, that'd be perfect for my netbook, and almost all the software I'd need there, will highly likely be present in the repos.

And for the main laptop, I guess I'm staying on Fedora KDE, unless I need my FL Studio and flash Windows back. I'll be figuring out where performance sucks, some bottlenecks, and fix them.