Hi there, some good advice there, personally here's some stuff I've learned over the years.

To get it to be in the right ball park I generally set it up more or less as the books suggest, then start it get it warmed up and try to accelerate, i keep tigthening the adjusting nut till i hear the clutch slipping, once it starts slipping I back the nut off about a quarter turn.

I bought one of the older style clutch gap tools, a piece of alloy with a slot cut in it for measureung the clutch gap, for me this was quite in consistent. I now have a old set of feeler gauges with the common clutch gap sizes, and a slot cut in the feeler gauge so u can slip it between the screw and the thrust bearing, it's quicker and for me more accurate.

Keep an eye on the bearings in the clutch Bell they are very small and get hot so can fail easily.
Another issue ive had is, u set ur clutch up and cars good but as u go through the race day car goes a little off and its hard to figure out what's wrong. Check the adjustment nut, I've had mine back off slightly, it never comes right off but backs off maybe quarter to half a turn just enough to make it drive poorly but not enough to immediately notice and pick up on. I've seen people loctite then on even slightly make a mark on the threads so it won't loosen off.

I don't often change the gap as its quite fiddly and not something I like to do trackside. But when i have messed with it to me a larger gap had a somewhat similar effect to tightening the spring, later engagement. Also been told not to clean the clutch Bell with brake clean as the build up of residue actually helps it. Could be nonsense though