1000% agree. I am disappointed [1] with JetBrains' attitude to this problem. They seem to judge anyone who isn't using the JDK11-based JBR in 2020 as a difficult customer, and do not acknowledge latency/lagging problems on Linux. Mac users then reply to threads like this saying "works on my computer flawlessly, I don't know what you're talking about", until they confess to being Mac users.
I have tried JAOTC up until JDK16 with some IntelliJ products, but I think you are right in saying that the single most effective knob (or two) to twiddle in the default installation is to enable ZGC and increase the heap size.
Yes, I know JBR provide DCEVM builds (which need to be enabled by downloading the JDK and changing the "boot java" setting, ironically)
[1] and by that I mean "fuming"
Yeah, vm options tweaks still don't cut it for me on my projects, and I've optimized pretty hard. Threading is the killer, esp. when connecting to other processes it can get all tangled up.
With a slightly larger max memory setting than default and using at least G1 garbage collector (ZGC for even better results) they would get a buttery smooth editor, but it is configured quite badly by default.
Though sometimes they just have threading issues, which won’t be solved by above.