Well, X-T2 cannot sync with flash at 1/8000s or even 1/1000s, while X100 can sync at 1/1000s.
You may use electronic shutter that doesn't depend on F-stop value (but it doesn't work well with flash or moving subjects).
Speeds faster than 1/1000 is not supported at F2 (and AFAIR 1/2000 at F2.2) in X100* lens for mechanical reasons (so, cannot be fixed by firmware, sorry). And this is exactly the reason why ND filter was introduced.
My X100T was with me at winter Altai Mountains bike ride -- few hours each day at -10C..-18C. And I kept the camera in backpack, in a plastic bag.
Moscow weather is much milder