Is the difference just the number of believers? To loosely paraphrase Sam Harris, if you believe some magic words turns your hat into a cat you are delusional, but if you believe saying some magic words turns a cracker into the corpse of your long dead leader, you're just Catholic.
I was raised a Catholic.
I did not meet one person who believed the cracker was more than symbolic. Some saw it as kind of sacred. But people actually believing the Medieval stuff?
No.
I am not a big fan of Sam Harris.
But the issue is certainly prevalence of a condition in the population.
Being a Catholic is not a condition.
Who you want to have sex with and what gender you identify as are. Almost all people have a sex drive and some kind of gender identity.
Some delusion you are a bowl of spaghetti is a problem for a psychiatrist.