Whether it would be OK is a huge unknown. Some retailers swap out springs (and leave the original in the box) to keep them well below site and legal limits. With those that don't, the +10% variance out of the box puts you far too close for comfort in terms of failing a chrono test.
The Krytac P90 has a quick-change spring so you can drop in a lower power spring easily. You won't need to remove the gearbox from the gun, let alone open its casing up. Just bear in mind that M*** springs are not completely standardised so you will see variance in muzzle energy between the M100 springs from different manufacturers. On top of that, the compression and air seal within the cylinder will have a big effect so working out the right spring isn't an exact science. M100, M95 or M90 springs may be suitable.
Whichever spring you use, I would leave in some head room to account for very small differences between chrono test readings - it's all too easy to chase a limit then find yourself over it when you come to the chrono ahead of a game.
The Krytac model is largely proprietary so if something mechanical or electrical goes wrong, you'll either be locked into Krytac's ecosystem with spare parts or you'll need some expensive tech work to get it back up and running.
I would also suggest saving up for a chrono for peace of mind so you can go to a game with something you have a good idea will pass.