So essentially what I'm doing is thumbnails for my yt-videos, the scene itself is my logo & a video episode number (geonode thing that generates number outline, etc, all I need to do is change the number in geonode settings).

Essentially:

the ground "plane" is a shadow catcher.

Then in compositor I want to add eg. game logo & some screenshot/relevant scene/background from game -> position/rotate them (separately) -> done. This is essentialy once-and-done.

Occasionally the logo and background don't play nicely, so the logo needs some dropshadow, for this I sometimes just use the logo's alpha to make a black version of it & offset it somewhat under the original logo.

(the left-corner of the first word of the logo)

And this is where the cropping issue can happen. And as stated in op, I could add padding to the image, but again extra step OR do it logos/backgrounds in gimp.. etc etc, there are out-of-blender options, easy ones. But: Ideally I'd want to automate everything for the ultralaziness. :)

edit: I did at once point add the logos as planes in the scene (as seen in the object outliner), but that was bit fiddlier than just dropping them in place in compositor, and similar "dropshadow" issue still existed, kinda. Some offset second plane does work - kinda. But logos tend to vary in size and aspect ratio, so it becomes fiddly rather quick - the compositor is easier in this case.