Is it going to be a lower percentage of the total population though? There's a lot about ye olde days that kinda gets generalised, and hand-waved. Like people's ability to read in medieval times. Sure it wasn't as prevalent as today, but reading was probably a lot more common than most people think.
As for belief in mythical beings, who knows, religious belief was a lot stronger in the 1700s, but that doesn't necessarily mean everyone believed in the fae.