Not exactly expert advice, but lots of long hours logged...

Like Steve I also run type 3 and type 6 or 7 DC tips, but 12'6" in length, in 6, 7, 8 and 9 weights. I settled on tip lengths of 12'6" because I can use them on all of my rods, 11'6" to 13'6", making only minor adjustments to casting stroke per given rod.
I carry a couple T-11 tips "just in case", but haven't used them in years.
I typically run un-weighted to lightly weighted flies, year round. In unfamiliar runs or runs with constantly changing features, I usually start in with an overdressed fly (rabbit strip), removing parts of the fly while stepping through to get it to do it's thing just right.

1) You should use what feels good/right to you.
2) Yes to more time on the water.
3) I don't change line or tips per run being fished. Instead I'll just adjust fly density and delivery angle, to afford desired speed and depth of swing.
4) Hard to know for certain.
5) Zero down time is a dream. Unless fishing the exact same piece of unchanging water, day after day, year after year.

Sounds like you're finding fish just fine, so have fun with the tinkering.
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