what type of bike/frame to use when overweight?
Old-school racing bikes (I have two) are not as comfortable as old-school MTBs when you resume riding, especially if you have a bit of a gut. The upright riding position that the vintage MTBs offer (or a modern equivalent) is one of those things that can keep you on the bike until riding a road bike becomes more comfortable.

When I resumed riding (as a middle-aged adult), I was fortunate to get this at a local garage sale for $20:



With the benefit of hindsight, I can tell you that had I resumed riding on an old-school racing bike, I would have certainly quit. I was way out of shape, and the bent-over position required for riding a road bike would have been so uncomfortable that there is no way I would have persevered. But this Peugeot was just what the doctor ordered, no pun intended. I rode it for about 1,400 miles (about 2,250 km) before upgrading to the old-school road bike.

Of course, YMMV, and you didn't mention your height or your age.

BTW, one of my old-school racing bikes has Tange #2 tubes and I am still around 200 lbs. I put about 1,500 miles on that bike, for what it's worth.

Final thought: you may find this subforum helpful. There are (and have been) many folks in the same boat.