Thanks. I really appreciate the lesson. I was pretty confused. The square staggered tile in the pic, would you say it's 6x6 as well? Thanks!!

6x6 is a pretty common size for wall tile. Lay it straight or staggered, the choice is yours. Standard ceramic wall tiles have built in spacers on the tiles that allow you to butt the tiles side by side for minimal grout joints. Porcelain tiles that are 6x6; non rectified will need a minimum of 3/16" grout joint or rectified minimum of 1/32" grout joint.
Also keep in mind that there are natural stone products that come 6x6, most of the time tumbled. You have tons of options available to you in the 6x6 size.

Thank you. I'm going to assume that the square white porcelain tile in the pic above (staggered) is 6x6z

Yes.

Thanks