I layout my front (or rear) panel on a drawing program. Then I print it on a normal printer (any). You may have to play with the program to get a true 1:1 from your printer.
Tape it onto the front panel and use a small pin punch to mark the hole centers and corners of any not round holes.
Then for the non round holes I scribe a line on the panel between the dots. I use a sharp exacto (backwards) as a scribe.
Likely for the USB and Power in you show, I would drill a hole then I would only have to file the corners.
Any step drill will work. They are wonderful! I usually color the steps with different color markers so I know where to stop drilling. They are not cheap but for only plastic you could start with a less expensive one.
I personally don't use a nibbler often. They leave marks on the panel, especially on a softer plastic (abs).
Dremel's can be useful but they are hard to control by hand.
Greenlee has different punches for odd shaped holes, RS232 Sub D etc but they are costly.