hi, and welcome
billing etc, your best to DM @johannes directly if there is an issue.
pots - I think most use 10k Linear, see this post for some suggestions.... also you can search the forum, and you'll find more suggestions.
EDIT: btw, make sure you also have some header pins (details in above post) as the axo board is 'bare' and you don't want to be soldering directly to the board. (male or female is personal choice, just get the matching jumper cables)