Do the Marble Blast Gold levels play identically in PlatinumQuest?

I'd prefer playing the Gold stages in PlatinumQuest for uniformity. Original menus aren't important for me at all, everything else looks the same in PQ.

Pretty much yes, aside from the addition of camera paths for PQ's level select the Marble Blast Gold levels in PQ use the exact same files and code as they do in MBG. I believe that the only difference at all is that the marble's radius is ever so slightly different between the two games, but it's not enough to be noticeable (it's something like a 0.001-0.01 radius difference between them, I don't remember).

That being said, I'm pretty sure you're required to use MBG if you want an official world record. If you're not on that level, speedrunning-wise, there's really no reason to care.

There are some minute differences that play a huge role if you plan on going for world records in MBG. In PQ's MBG stages, finish signs sometimes are in different places, some misalignments are corrected, and one of the Monster Speedway levels has an extra usable Super Speed.

CylinderKnot wrote: Some misalignments are corrected, and one of the Monster Speedway levels has an extra usable Super Speed.

This is completely false. The current version of PQ features MBG levels exactly as they were in MBG, and if you don't believe me, you can compare .mis files between the two games. If there are any levels that aren't completely identical (minus camera paths and tiny float rounding differences), let us know because that is not intentional.
While it is true that some versions of MBP originally featured MBG levels with misalignments fixed, these fixes were reverted at some point before PQ's release.

It's undeniable that there are some clear differences. Several start and end pads in MBG are sunk into the floor (like Learn the Super Speed, Tornado Alley, and Monster Speedway) while all of the start and end pads in PQ's MBG are at the correct heights. There are other differences too, like the moved finish sign in Learn the Super Jump and the downwards pointing sign in Free Fall.