I'm shooting from the hip, without diving into actual specs and such, which would be tough to do since we don't know what year models we're comparing here. That is not a criticism of the OP, that is me looking for excuses for shooting from the hip.
I'd be surprised if any Team Miyata was heavier than any Miyata 1000. So I doubt it'll be heavier.
My impression of the Team Miyata and Pro Miyata is they were not models that started as Euro-flavored stage-race frames, then morphed into US-flavored crit-race suffer machines. I think they sprang forth on the world as tight, quick-handling race frames for short/tight circuit racing.
Stiffer/livelier/friskier can be fun. Just understand it won't be a stiffer frame on the same width tires you're likely running on the 1000, it'll be a stiffer frame on probably much narrower tires. It's not just about the frame, it's also very much about the tires. Again, I don't know exact specs, but you're very possibly maxing out at 25mm tires on a Team. The _idea_ of stiffer/livelier can be great, whereas the _reality_ of stiffer/livelier on 25mm tires on crappy pavement may not be so great. I'd be budgeting a goodly amount of dough for the nicest narrow tires I could find. If they'll fit true 28mm tires, I'd dial back that warning quite a bit.
But as Mr. Spock once said: "After a time, you may find that 'having' is not so pleasing a thing, after all, as 'wanting.' It is not logical, but it is often true."
I agree with what you say. My 83 Super Strada has the same Miyata frame and 25mm tires on it. Just by looking I don't think 28s
would fit on it.