[rcxdude]

The issue is, if you don't have swap, then it's not matter of prioritisation: there are some things in RAM that can't be pushed out, regardless of how unimportant they are (so the only recourse is to terminate some processes, usually the ones using the most RAM. Linux the kernel by default tries really had not to do this, which is why there are userspace applications like earlyoom to do it, which is probably the better location for such logic).

And yeah, you can adjust the priorities and the latency/throughput tradeoff (even per-application to some extent), but it's a difficult thing to get right in general (what works for one use-case might make another a lot worse). I don't know of any DE that really tries to adjust this, though (not because the kernel can't, but probably because no-one on the DE side has really prioritised it or they have tried and it hasn't made a noticable difference).