FileBot

I'm running FileBot along several other processes and it can happen that load on the system spikes during post-processing.
Are there some options or settings that can help keep resources used by FileBot (not just RAM but also CPU and I/O) as limited as possible without breaking anything?

With SystemD there's the obvious choice to limit all of the above but I wouldn't know which limits are acceptable.
For other systems more intricate methods with ionice, nice and -Xmx -Xrs or even more exotic options.

You can use the nice command to run commands with lower or higher priority. If you set a hard memory limit with -Xmx then FileBot will error out if it needs more.

Is there a lower requirement? I mean, is 64M of RAM, for example, enough to do anything?

Depending on what you're doing, 16 MB is enough (e.g. simple -rename -list --q command). A typical -rename command with series auto-detection and episode matching and a custom Groovy format expression will require at least 64 MB and maybe more. The amc script probably won't work well with less than 256 MB. If you process a large batch of files in one go with the amc script then 512 MB and more would be good.