that would be a shrader valve Yes. the gauge goes up n' up vs. bouncing.
As far as unhooking the fuel line, it's kind of silly to attempt this without just removing the tank and airbox, but whatever. You may need to use something to hold the butterflys open on the 3rd gen (fly by wire, they don't always open when you twist grip)
Looking for consistency between the cylinders. If you have low or high readings, some gauges can read a bit differently too. 15-20psi differences in some gauges. i have a $35 autozone one that reads 10psi lower than my friends $200 Snap on.. so i just keep that in mind
agree about a leakdown. do both, or ld is better. Just a little more in depth and little more "know how" needed. comp test is pretty darn easy, gauge is cheap.