Cheers, yeah I've used Chrono24 once... maybe twice. It's a bit more like eBay, since it's a platform for private sellers and dealers rather than a standalone reseller (like Hodinkee, WatchBox, etc), meaning you're sort of at the mercy of whatever random individual/business has the watch. But C24 does supply some security via escrow. The one experience I remember---a few years ago---wasn't great: bought a neovintage Glycine from Italy and when it arrived it was running incredibly fast---like gaining more than an hour a day---even after demagnetizing and ruling out that possibility. Probably an issue with the spring. Anyway, I'll spare you the details, but I had to negotiate an international return with a skeptical (but I think fundamentally honest) seller, and C24 wasn't very easy to work with.
Not saying I wouldn't use that platform again---I check it all the time---but, as with eBay, you have to keep both eyes open and understand the potential risks and hassles. You also have to learn to use filtered search so that you're only seeing watches that are actually in stock. If you don't do this, you'll get many results (sometimes a majority) that, if you look at the fine print, say "item needs to be procured" (lately expressed as "ships within 30 days," or the like). Meaning the seller has posted a bunch of pictures and written a convincing listing, but doesn't actually have the watch itself: you click buy, you send your money, and then you wait---potentially weeks or months---potentially until never never---while they try to "source" a similar watch for you. It's not technically a "scam," but it's VERY shady, and I wish C24 wouldn't allow that. So... be careful with that site!
Sometimes if I find a watch I like on C24 (that's clearly "in stock") I'll do a bit of sleuthing and find it listed elsewhere---if it's a dealer, on their own direct site---and will go that route instead.