Will electronic stores accept either 100 or 200€ bills when purchasing an iPhone for 1500€ upon paying in cash?

Having worked in one - yes, it’s no problem at all. If it’s too much (I think 3k was the threshold), a manager has to come and do a second run in the counterfeit detection machine, so it might take a while.
(Answering for Germany though, might be different in France)

I work in a small store, we get about one to two customers a day paying with it.
When I worked in an electronics store, we had much more of them, but it was obviously still the lowest amount of all bills.

So I wouldn’t say they’re uncommon, but of course they’re the rarest one to get. Not only because ATMs don’t have them, but also because people rarely withdraw 200+€ on a regular basis in the first place.