Hi funcitypapa, and welcome to SFC.
I've only been collecting US stamps for a few months, pre 1940, so at the moment I'm working on Scott 600 - 900, working my way backwards from 1940. I collect MUH and only very well centred, so XF+. This of course is a real challenge, for one thing I buy every stamp individually and not in sets or groups, so I can select only well centred with no faults. The other problem is finding a well centred stamp that hasn't been graded! It's a real pain, as you scroll down lists of stamps, see a well centred one, look at the title and price, and sure enough, PSE Graded 98 etc, $575 for a 20 cent stamp. You can't even see the difference with the naked eye between a 95 and a 98, but the price difference!
What really annoys me about this grading thing is that the exact same stamp without a graded cert. would sell at around CV or a little more. What kind of a basis for stamp pricing is that? A superb stamp should be worth a certain amount, not dependant on whether it has a grade or not. How can you put 2 stamps side by side, that look absolutely identical, and say this one is worth $1, but this one that you can't see any difference is worth $500 because it's been graded.
I am prepared to pay more than CV for a superbly centred stamp. That's always been the way, premiums are paid for superb examples. I've found I don't have to resort to this that often, as I can usually find perfectly centred stamps (to the eye) at normal prices. But on occassion after much searching if the only stamp I can find is priced higher because the seller has labelled it "gradable" or just put a higher price on it, I've paid it, usually up to 5 to 10 times CV for the cheaper issues (so like $2 for a 20 cent CV stamp.) So far I've only purchased one PSE graded stamp. I do have a few on my watch list if I can't find similar.
As for your other questions, I'll refer to my other collecting interest, which is the Australian colony of Victoria, so 1850 - 1912. Where possible I will pay for MUH. That's just always been my preference. However this of course is not always possible, so some of my stamps are hinged OG. For stamps that are worth $1K+ I'll often get used to space fill. I don't like the idea of unused NG and have never bought any, even when I've seen some that look great. One reason being the same as you mentioned, that it could be a used stamp with the cancellation removed. The other reason is that the stamps were issued with gum, so that's just my preference for collecting them. To me they're not whole if they have no gum. Eventually I may have no choice though.

Quote:
You can waste time at work like we do!
I'm at work atm.

Stuck in the office on light duties still, but at least I have plenty of time online.
Balf