Ye Olde Inn

The tiles I got from both NA versions are thin with white backs. Is this the same from the EU versions and/or other NA versions?

Mine are very thin as you described for NA

The EU version I have - Dutch - has black backs and they're fairly thick.

As I understand, the EU ones are as thick as the Base game tiles. I'd love to get some of those one day.

European version tiles are ticker and with white back. KK squared tiles are about 1 mm larger than WL tiles.
US version tiles are thinner and feature a white rear side.
If anyone got black rear tiles (instead of white) they are taken from the main game or other expansions.
I did a guide somewhere about this...