Would be nice if there is a tool for easy making round holes in a plane.
Any suggestions
depends, show what you are trying to achieve. There are ways to either add a circle that has the same vertice count you want and bridge the loops, you can simply use the looptools addon to make a circle from a selection of verts extruded from your face, and either way I would like to emphasize that making a custom orientation from your selection can make all the difference.
Oeps I forgot modifier - boolean. Works awesome
Add cylinders - select modifier boolean - settings see picture and choose apply.
that works, but check your mesh and see if you need to fix topology afterwards.