That means you first have to trade with BitPay. This third party buys the BTC from you (that Breitling doesn't want, okay?) and may or may not (depending on market conditions, crashes) give you a varying amount of USD/EUR for it that Breitling then takes. You might as well sell a car first for dollars to a third party and then buy a watch for it. That doesn't mean the watch seller now accepts cars. Even speeding up the process by a software platform doesn't materially change this.
It likely is instantaneous. Same difference as using CC's overseas. You want to split nano hairs, go right ahead.
There are enough who have the means and motivation to afford luxury products but who are currently not able to get their hands on foreign fiat in exchange for their own restricted currencies otherwise those luxury makers would never offer to accept crypto currencies. There is no other perceivable reason to make such a move. Luxury makers are not in the business to worship every temporary and short lived fad but they obviously realize that various financial transaction sanctions are biting into their sales. What other reason might there be to take such step? So that Johnny Crypto can now cash in on his bitcoin appreciation? I highly doubt that. Another 20 or 30 percent down in BTC and I guarantee you that we will never hear from @johnarb and his ilk ever again. They are definitely not a target clientele for the Breitlings of the world.
Big difference here because then you're trading a currency for a currency. Both currencies are also being used in their own right and directly as such in the respective regions. Unlike first having to sell a pseudo-asset that's pretty much nowhere being accepted directly as payment for goods and services.
Not even close! You can't sell 1/2 your car. If they are accepting bitcoin as payment at the going exchange rate it is no different than accepting euros or Canadian dollars. They convert the currency to the one they are using. Bitcoin is considered by the merchant as a foreign currency. You couldn't spend part of your car to buy that watch.
Sorry, no difference at all. Only in your mind. AMC Movie Theatres, Gucci, Starbucks are just a few of the businesses that now accept Bitcoin.