Frankly very stable, I’ve been using it since before it was EndeavourOS and in all this time I’ve only had a couple of bad experiences (at least one was entirely my fault). With that said it’s a rolling release so if you’re using it for anything mission critical don’t update unless you know you have the time to fix it is things go wrong. Now I don’t mean don’t update as in never update, I mean don’t update it daily (or like some of us who have OCD hourly). I use EndeavourOS a couple of servers at home (a media server and a home grown NAS) and I basically update them monthly, and they are vary stable.
That said always have a USB key that you can boot off of if you do have issues, and if you use BTRFS make sure to take take snapshots before you make updates so you can always go back to a previous state. Take the time to learn how to do that. You won’t likely remember when you have to do it, but having done it at least once or twice will give you some muscle memory the next time you have to look up the steps.
I have been running both a custom PugetSystems desktop and an HP Spectre laptop for a couple of years now with only a few update problems requiring manual intervention. I use pretty traditional Linux features (no btrfs for me) with a customized Xfce desktop, dual-booted with Windows. It has been a very stable system, but then I only update every couple of months, so maybe I missed some problems that others have had. This forum is great for finding solutions to problems. I’ve been very pleased with EndeavourOS.
Well the fact that you also play videogames might change things a bit. I use my install mainly for development and/or tinkering. I have no clue how it might be for gamers, maybe someone else here can attest to that.
I would say there is nothing wrong in sticking to a mainstream distro. The only reason I ran away from Manjaro was the constant fck ups and mismanagement of their repos in regard to the AUR and the only reason I use Arch at all is the AUR itself.
I haven’t read about Manjaro drama for a while, I’m guessing things are better now.
Regarding the RAM usage, I would say the distro has little to do with it. The DE is likely to be a much bigger factor here. Gnome (the default for Ubuntu and PopOs) for example is a bit of a RAM hoarder and KDE is likely not much better. But you can install other light weight Desktop Environments in any distro you want (even if it already comes with one by default). In fact I’m pretty sure you can install Manjaro with all sorts of DEs or Window Managers.
And regarding customization I would suggest you don’t stress too much about it. Linux allows you to customize pretty much whatever you want, although some DEs are friendlier to that than others.
I would suggest you worry about functional customization and not as much about what does or doesn’t look pretty. That stuff you can always do by yourself with a bit of free time.
From what I’ve seen, gamers prefer Arch Linux because of the AUR and the fact packages are updated very frequently. EndeavourOS doesn’t strain that much from Arch, so it is a very good for a gamer. In my experience, the performance and usability was great on Endeavour and it should be much more stable than Manjaro’s weird package delivery model.
Frankly speaking, I was opposed to rolling release systems for the long time.
I decided to give EOS a shot 4 months ago and haven’t had a single issue since then. What you might take into consideration is you need to update regularly (once a week is enough in my experience) and have backups in handy if something goes wrong and you can’t fix it (which doesn’t happen often).
The stability also depends on some of your choices during installation - especially kernel (if you don’t use the latest hardware, LTS is enough), filesystem (ext4 is ol’ but reliable) and DE (Cinnamon and Xfce might give you probably the most stable desktop on Linux).
Stability also depends on what the user does to their installed system. Hardware does make a difference keeping the UEFI firmware updated. It also depends on the manufacturer as some are better than others with linux grade hardware and updates.