I only own 1 Solwin Module called “Attribute Tooltip and Image”, purchased in Oct '17. Looking at my email history I did have a theme compatibility issue with it - But they patched it for me within a week. I never actually got around to pushing this to our Production site… Mostly because I forgot until now. So, I couldn’t give you any more feedback than that I’m afraid. Although, I suspect I’ll be installing this in the near future - If it still works.
I highly recommend GTM. I use it for all of my projects. I’m currently using their Enhanced Ecommerce Module. It works really well. However, learning how to use GTM effectively with GA will probably take a few days