My SO is from a Catholic Latin American country.
There are rules that I would need to follow if we were to marry in her country. I'd need to promise to respect her faith, and that any children would be raised Catholic, for a priest to marry us, that kind of thing.
Her family are moderate so its been pretty easy for us though, most religious stuff comes from cultural differences that are based in religious ideas. These can be a mix of Catholicism and indiginous belief systems.
For us its like "this is a thing thats different", we just embrace stuff. I'm aware that our religious backgrounds are close so it will make it easier.
I've known people from very different regligions who have married too, I think if people are open minded and respectful, it works. Family might be the biggest obstacle.