My questions to C&V will never end.

I'm now kind of confused with old Raleigh sizing. I'm kind of restricting my Raleigh search to the good and above average frames from the 70s or so. International, Competition, maybe Super Course. Most likely the first two.

I see that in some years, for some frames, the smallest size is "21 1/2 inch".

Some years they offer a smaller size "20 1/2 inch"

I currently fit very comfortably on a bike w/ a 54.5cm horizontal TT, a 73.5 degree seat tube angle, 72 degree head tube angle, and 90-100 mm stem. I wouldn't mind going a little longer on the stem, if the frame had a shorter TT, but would prefer not to go shorter.

In terms of stem length, I could certainly go down a frame size, but on my modern bike, I like the taller head tube on a ~54cm frame compared to a ~52cm frame. I could make it work with a high rise stem, but it 54's are usually the sweet spot for me. I do know that a ~56 cm TT is too long for me to be comfortable on, not only because the stem's getting pretty short, but it just feels too big all-in-all.

I think the head tube issue could be negated w/ an older frame because I could raise the stem much easier. So, I'm more open to a smallish vintage threaded headset frame than I would be w/ modern threadless headset frames.
So I was thinking I should fit fine on the 21 1/2 - it's about 54.5, certainly less than 55. But now I'm to understand that the TT on those frames is more like 56 cm (gotten that from a couple of sources).

What do you think, those of you who are familiar with these frames? Should I limit myself to the 20 1/2 (which are much more uncommon). Is there something about any of the seat tube or other angles on any of these frames that might mitigate this top tube length issue?

Thanks for any advice you can give.