ok, say your target is 100 ft away, your gun at 450 FPS would take .22 seconds to get to the target. Now take it from our max FPS of 400FPS and it will only take .25 seconds to get there, now im pretty sure you arent going to notice .03 second difference.
as for range (I'm assuming your using a .20g BB) at 450 FPS (1.9 joules) using a .20g BB being shot from the shoulder would travel about 204 feet before hitting the ground, now lets say your gun shoots 400fps (1.5 joules) with the same BB and conditions, its effictive distance should be around 182 feet, now a 22 foot distance isnt that much not to mention thats max range before it hits the ground. I highly doubt that that at 200 feet there is any accuracy, its more just luck.
Now there are a lot of varibles to the equation i used, and it doesnt account for a hop-up. theres also things like wind, elevation and many other things that would effect the porabola, but for the most part at long ranges an extra 50FPS isnt going to be that huge of a difference.
And as for the muzzle velocity reducers, true they arent 100% static and proven to always reduce your FPS, but [in my opinion] who is to say you can't just crono in an hour or so before the game starts with it on, then before we start playing just take it off.