I looked at many different techniques for the fig graft and as you say, this v shaped cut seems a decent system. I even went and bought a special grafting knife just to make the cut nice and clean. Don't forget to take the moon cycle into consideration when choosing the correct moment to make your graft. Unknown to most this is a very important factor: https://peakd.com/hive-140635/@samstonehill/bud-grafting-with-the-new-moon-to-create-a-multi-variety-fruit-and-nut-tree
Have never tried air layering, but you can be sure I will be trying it this year...
Best of luck with everything!