Just an estimate, also the 2 probably never existed and even if they did amphicoelias would have to have very light but sturdy bones.

in a nutshell, bru would have heavier bones then amphi?

Maybe, Maybe not. I'm pretty sure the estimates vary greatly concerning the weight of Bruhathkayosaurus so I think it's better not to dwell on these things.

Bruhathkayosaurus is likely fake, while Amphicoelias likely is nothing special.

sorry to cyber-necrobump, but Bruhathkayosaurus is probably a fossilized tree, and not a tibia at all! Amphicoelias existe, amphicoelias altus, that is. amphicoelias fragilimus could or could not have, though. Fragilis' bone was the only one found, and it crumbled away. This makes people think it wouldn't have existed, but I think that it did. Amphicoelias bones were probably crumbled away before we got to excavating them, and maybe the found specimen was just really strong. It will remain a mystery for years.

There were Argentinosaurus sized dinosaurs that weren't fully grown, so I think it's entirely possible for a sauropod to reach 190 feet.

I guess I think so too.