I have a laptop with 4gb ram that i've been using kde plasma on and fairly frequently it just freezes or I have to restart because I had like 6 tabs open in firefox

Although I don't remember having that problem as much when I was on xfce, but I also might not have been using it as heavily then

I've never had a similar problem with chrome on chromeos with the same amount of ram, I think chrome+chromeos might be more aggressive with unloading tabs

Sometimes it does actually kill firefox but sometimes it just becomes very slow (1-2 seconds per frame) or freezes entirely for several minutes when out of memory. Might be just because the swap is really slow, but there's just 2gb of that, why would it freeze for several minutes? (One time this was happening was when I was trying to compile llvm on two threads, I ended up having to temporarily kill the desktop environment to save ram)