In recent years I've becoming am amateur student of religion, you might say, and jave worshiped at over 175 different ones. These have included everything from Mormon to Muslim, Baptist to Buddhist, Jewish to Jehovah Witnesses,
I try my best to follow whatever others do, except when they conflict with my own faith. I consider that good manners as well as respect for other faiths, which I possess. I am not one who easily accepts the idea that only one church has the full truth. That sort of arrogance has caused so much bigotry and worse over the years. It resembles the position of the Islamic crazies, and I want no part of such an exclusivistic point of view.
Now, as far as mainline Protestant churches go, I find them extremely open - that is, if a visitor genuflects that's fine, though the members won't do that. They just assume you're Catholic and will likely give you a special welcome. Most of them practice a 'big tent' approach to religion. "You go to your church and I'll go to mine, but let's get along together." They just don't go along with various doctrines and practices, whether they concern Mary, transubstantiation, priestly celibacy, praying to saints, etc. I find that their personal theologies differ from one to another and that they are divided on issues such as abortion or same-sex marriage.
Evangelical Protestants, however, who number about the same as mainstream Protestants, are usually even further away from Catholicism on doctrines and practices, but on social issues like abortion or same-sex marriage they take the same position.