I don't have any special expertise re: design - however, I thought that a "Provence inspired" or French Country style has larger and/or irregular grout lines. Typically natural stone materials are used which can often lead to irregular sizing which adds to the rustic/charming look of the style.

But maybe I am wrong . . .

I’m a big fan of this tile from Virginia Tile called Petra di Ostuni - it comes in a greyer colorway (this is the warmer). It’s a porcelain but looks like limestone. It also comes in a small scale matching tile that you can use on your shower floor so you have visual consistency:

I think you’re right on the larger/irregular tile. I’ve also seen some that are more like that, but was wondering if something like this might give a stone look with a little less rustic feel. Thank you for the comments!