I am using 12.2 and very good it is, but I can’t find a way of changing the resolution of the grub2 boot menu. It did adjust itself to a sensible, good looking resolution after a recent update but has changed back to a really low rez look again a few days ago.
While it may be a nuisance, I would not be too concerned about the boot up resolution if everything else works as its much more important. So do not go crazy changing things to fix this issue is my suggestion.
And if you do have something more serious, do let us know. I still would check out my bash script grub2cmd for Grub 2. It provides some nice help with making changes to grub 2 operation.