My fastest grab speed ever in the new Legions was on Moonshine. Something weird happened involving me capping and a bunch of defense (no HOF), I managed to grab the flag at 299 (you can ask Sid). My fastest cap route is on Zenith and it averages about 270, but I always miss because it's really hard to adjust in the air going that fast.
O, btw my fastest grab and cap was 317 on Zenith. While I was coming in at 200+, Sugardemon overdrove me before I hit the stand and it somehow accelerated me to that speed. After I grabbed, I had to slow down and turn to stop myself from running out of bounds.
That is one hell of a fast route on Zenith!
I figured by now everyone knew this route. It averages 220-240, but I've got as high as 276. From the other side of the map I can only hit 250.