I did that and went from 24 to 44. I got emails to choose additional perks for reaching 30 and 40 tiles, but when I clicked through they weren't available. That makes sense to me, but they probably shouldn't send emails if the perks aren't really available.

I should reach 50 soon due to flights. Will that make me Mosaic 1 for 2024 (I'm already Mosaic for 2023)?

It also seems like you need to pick your perk quickly or it goes away when you reach the next level. I didn't pick after 10K and looks like that opportunity was forfeited.