Couple of comments: 1st on Euron's fast-travel, you are still assuming that we are being shown things in a linear timeframe. We're not.
Case in point the whole Sam/Jorah surgery thing was shown across 2 episodes, which covered (supposedly) a few days in the Citadel. In those same 2 episodes, Jon somehow made his way from Winterfell, to a shore, to Dragonstone, a trip that in the established world should have taken a week at a minimum, and more like 2 or 3. (Remember back in Episode 1, it took Robert and crew a MONTH to get from KL to Winterfell, and that was more or less straight shot). Also, Bran somehow traversed the 630 mile trip from the Wall to Winterfell in those same 2 episodes.
So, not linear time. Euron may have met with Cercei a month before we see Yara's fleet leave. Giving him plenty of time to skirt around dragonstone and simply wait to ambush her fleet in route.
Also, Quentyn Martell is the biggest waste of a story line in the books to date. Sooo much time and energy on some rando dude who ends up being absolutely worthless to the plot of the book other than to establish he's not blood of the dragon. Just ridiculous.