ctrl-f10 for releasing the mouse is the one menu won't help you

ctrl-f11 and you will only need ctrl-f11, ctrl-f12 for adjusting speed in most cases
ctrl-f12 so three in a row and the first one you know

ctrl-f1 allows checking all available shortcuts at any moment
as for the cpu settings always use dynamic core and if the game doesn't use max cycles just adjust them with ctrl-f11/f12 - that works for most games
windows scaling and filters
fullresolution=desktop
windowresolution=original
output=openglnb
don't use filters they always look worse
Capture for videos
just copy the files later to wherever you want
Drive for mounting
you can install games in separate folders so you can always use the same folder for mounting
you can also edit your own small dosbox.conf with only the most used settings so you can access them easily