I usually shower at EVA’s lounge, but it’s not part of Priority Pass. As far as PP, I’ve showered at Air France/KLM, Oman and Turkish. I usually don’t visit the Miracle lounges, and I’ve never showered in them.
I don’t usually eat breakfast, however, for lunch/dinner Oman is the best followed by Air France/KLM. The food in the Turkish lounge isn’t very good. However, the shower in the Oman lounge feels very close to where people are seated and for me doesn’t feel very private. Air France/KLM is probably the best of the three when combining food and a shower.