Okay, hear me out. You want to keep an eye on your system for things like RAM use, disk space, processor load and more…but you want something a tiny bit flashy that's still simple enough to run in a terminal window? You need to try out bpytop.
It's a fully featured resource monitor with a "game inspired menu system" and it's genuinely great, I've fallen just a little bit in love with it having it open on my second monitor to keep me informed of how my system is doing. Just look at how gosh-darn awesome it looks:
Thanks to the process selection feature, you can also use it to send "SIGTERM, SIGKILL, SIGINT" to individual processes if you need to get rid of them or if they're stuck. I can see this being incredibly useful. It does practically everything you need and it looks good while doing so.
bpytop is actually a port to Python of another project named bashtop, with the creator suggesting people move on over to bpytop due to it being faster, less resource hungry, mouse support, graphs for memory consumption and more new advanced features.
Their "game inspired" menu is a nice bit of fluff too, giving you a quick and easy way to adjust various settings - very much like you actually would find in a game.
The developer appears to have plans to expand it too with GPU support for temperatures and load, options for resizing all boxes, CPU and mem stats for docker containers (if possible) and the usual optimizations.
As a bit of icing on the cake, you can theme it too.
Check bpytop out on GitHub.