Specs on omni-wheels?

For the VEXpro omni wheels meant for FIRST competitions, the page mentions both the coefficient of friction and that the wheels are perfectly round.

Does the same hold true for VEXedr omni wheels? Approximately what coefficient of friction could I expect on tile (think school hallways)? Are the double-roller wheels perfectly round, or do the have slight bumps as they roll? How much sideways play does each roller have (could they be relied on for dead reckoning over distances of about 10m)?

They do have slight bumps as they roll because the wheel is not perfectly round. As for the coefficient of friction and the sideways play, I would recommend testing them on your own. The wheels should operate just fine on tile, though.

Are the bumps big enough that some of the wheels on an 0-drive (6 omni wheels arranged like a 0 on a 7 segment LED display) would lose contact with the ground (especially the 2 side-to-side wheels)?

No, assuming the drive is built straight.