Hi, only me again.
Set a custom action to 'toggle all FX on/off', such as Ctrl+F. It's very useful if you want to open more Reaper tabs or windows, eg for project/item copy/pasting purposes.
While the FX are off, your computer won't go into snail mode and Reaper won't be straining to even run. If you then minimize Reaper with all the FX off, it doesn't seem to hog CPU, and it's much faster to switch back, including turning the FX back on.
No need to close Reaper any more! I haven't tested to see if it reduces loading speed
YMMV.