These are all great ideas, but if you want the most professional, readable, permanent, and flexible solution, use laser engraving of special plastic laminate sold by Johnson Plastics and others. The laser can cut a profile for the label(s), cut holes for connectors to mount through, and label the connectors. The material has a self adhesive backing so you can peal and stick to the panel.

I use LaserMax Rowmark White/Black 2 ply 1/16" thick with excellent results.. You can see a picture of my panel he https://www.dropbox.com/s/q6355wzj96...label.jpg?dl=0 A single placard takes care of all the items on the right side of the panel. I plan to do the required placards as well using this method.

Ideally a single label will handle multiple fuses/breakers, USB connectors, audio jacks, etc., and the profile will match your panel. You need to generate the artwork in something like Adobe Illustrator, or the like, and there are many services that will cut/engrave for you. For example, Rex at WSC did it for me. As suggested, choose a readable font like Helvetica bold for clarity. You can print to paper to check alignment, etc.

Have fun, and be prepared to be impressed.

Matt Herron