In my playthroughs, delaying Byz's religion because you are guaranteed a religion was never a good idea. The sooner you found the sooner you enhance/reform and the easier time you have with spreading. Don't read Byz's UA as an excuse to slow play your faith, read it as allowing you to guarantee any synergy you want in your religion.
I've also found double founder to be the strongest for me. CoE + Apostolic and aggressive missionary spread was really powerful in my last game with Byz. I quickly became the tech and culture leader while my capital had the growth and production to just build everything including whatever wonders I wanted. It gets silly if you build Borobudur and Hagia- then your missionaries get extra spread for extra faith efficiency and you don't even have to stop buying missionaries to save for an enhancement prophet. You easily have the faith to pump out missionaries while also faith buying whatever buildings you need. This power spike runs out eventually once you've converted everyone (and the yields just naturally don't scale well in later eras) but you get so much science/production/culture/food in that early phase that I think it's worth it.
Having a dominant spreading religion has nice benefits toward diplomatic and tourism victories. Free votes from religious authority, easier time passing world religion, +tourism modifier from shared religion, etc.
I've also found double founder to be the strongest for me. CoE + Apostolic and aggressive missionary spread was really powerful in my last game with Byz. I quickly became the tech and culture leader while my capital had the growth and production to just build everything including whatever wonders I wanted. It gets silly if you build Borobudur and Hagia- then your missionaries get extra spread for extra faith efficiency and you don't even have to stop buying missionaries to save for an enhancement prophet. You easily have the faith to pump out missionaries while also faith buying whatever buildings you need. This power spike runs out eventually once you've converted everyone (and the yields just naturally don't scale well in later eras) but you get so much science/production/culture/food in that early phase that I think it's worth it.
Having a dominant spreading religion has nice benefits toward diplomatic and tourism victories. Free votes from religious authority, easier time passing world religion, +tourism modifier from shared religion, etc.