One mod in KSP1 i pretty much do not play without is RCS Build Aid, which (among other things) adds a tool to help place RCS thrusters by showing how much torque each thrust direction gives with the current RCS placement
It'd be nice to have something like this in KSP2 since you kinda just have to eyeball it with the COM and it can be a bit of an issue if there's something there that you can't place RCS nozzles on
Something like this for engines would also be nice, Micro Engineer has engine torque but it's inconsistent about actually displaying it
#RCS torque readout
past apex
low widget
Yes
weak sierra
also dry CoM readout