How do you finish a valve when using pex pipes
The pex usually goes into fittings that are set into the wall.

I used 1/2” elbow fittings well secured for two sinks and a shower. For the shower the fittings had to be on 153mm centres and a bracket was made for that.

Here is a link to the type I used:
https://www.hornbach.ch/shop/Raccord-de-serrage-angle-de-mur-16x2mm-1-2-IG/7011451/article.html