The Thrust frame looks like it uses a standard round seatpost, while the Tantan has a proprietary one. It would be easier to find a replacement for the Thrust if needed.
Threaded bottom brackets are pretty easy to work with, so that's what I'd go with. You typically just need one inexpensive wrench to install and remove.
Well I have 800mm of usable leg give or take. I plan on 170mm or 165mm cranks. so that leaves me with 630mm about, so with a 520mm seat tube. that leaves me with about 110mm left for seatpost and saddle. So around 5 inches. 6 ins with a 500mm seat tube.
So for the tan tan that gives me about 380mm reach and 550 in top tube length.
The thrust is going to be about 400mm reach and 575 mm in top tube. So about inch more for my torso...
the seat post is an worry too. but it will but the same for the vero build 218
the tt-x2 weight is probably 1900g and the thrust is about 1600g... give or take.
And I would be worried about delamination on the bb for threaded but the press does offer a challenge and a bearing press which you need for the front tube bearings anyway. right?