Some thoughts:  #WP policy of verifiability & NOR forbids any sort of interpretation of sources. Therefore statements that most Christians believe something must be based on RSs that say just that. #In other cases you might say all major churches believe, if that's what the source says. #If a source says most major churches, such statements should probably be excluded for lack of clarity. It means something totally different depending on whether the Roman Catholic Church is included. #You might use phrases like mainstream or traditional, but only with care to ensure they're not liable to be misinterpreted, & only if the sources use them. #WP:NPOV does allow tiny minorities to be ignored, but doesn't say how tiny.       