I know how heavy my FG is and it runs great on a XLX2.I don't think people take into consideration the WEIGHT of a system larger than 8S. The batteries alone could add more than 2 pounds to the car plus the ESCs are way larger. I watch tons of videos of people running 10S, 12S, and higher and the speeds they get can be obtained with 8S or even 6S when geared right. For 5th scale you NEED that kind of power due to the size and weight of the car without any electronics. Trying to squeeze that into a car made for 6S or even 8S is almost fruitless in my opinion. You weigh the car down and rob it of the characteristics that made you buy the car in the first place. I've only seen one person do it any type of success...I think he got over 80mph in a Kraton 8S off-road and he had the MGM setup in his. Check out one of his vids here:The other larger scale ESCs like ZTW and Flier seem like trash to me from what I've seen.
More voltage means less amps for the same power which is good for many reasons (less heat/stress on batteries/big can low kv motor matchup), but voltage alone doesn't bring power. My point is P= U*I.
And the XLX2 is 600A capable (at least for 10s bursts), disregarding ZTW and flier, only the 800A TMM 80063-3 outperforms the XLX2 in terms of I.
At least up to 12S, none of the 400A ESC's will deliver more power than the XLX2 at 8S. And with better ESR/small volume caps and castle software it will do it more efficiently. Adding more weight and volume (esc and batteries) just adds more load, reducing efficiency even more. So in my opinion unless you want to pay 1600€ for the 80063-3 you are always better of running a XLX2 at 8S.