Where I’m from, FPS stands for frames per second and had to do with image rendering. Not sure about you
Tick rate is the server’s state update/packet frequency
They’re not the same
FPS as unit is the same as Hz. its something per second. usually serverside the “rendering” runs at the same tickrate as the gameloop itself, sometimes displaying it in fps, as a “frame” is not always visual information.
Not saying it’s more correct, than Hertz, completely agree with u there. But it’s also not wrong.
@OP:
unfortunately, you run into a couple of problems in physics simulation at some point; you would have to look that up yourself, but here is a linkto a good start, if you really wanna know.
To break it down, the faster something gets, the less predictible is its rotation, and vice versa. That’s not completely correct, but let’s leave it at that. 700.0 is already a pretty good limit (in the scale of SC); It’s not the maximum of modern physics engines, but after all, the feel of speed in games is actually also dependent on the effects anyway, so its more about making the “range” fair enough.
@Cruise:
or just fix prediction if the differential / pre-capped speeds are higher than 700. because aim help seems to fail on cruise engines. works nice if you lead the aiming box even further tho, given you have decent ping. I don’t see a problem currently in cruise as an idea, as it still requires somewhat of skill to actually be useful to your team. However, cruise engine carrying a bomb should also lose its adaptives. Cruise could also reduce effectiveness of vernier engines, or vice versa. tackler inhibitor could do additional slowdown on cruise aswell. Or cruise itself could actually reduce normal speed, and only speed you up on ab. It could also have a negative collision damage modifier. 
But capping rot is also an idea, mainly it probably would only be to deal with rockwells and jaguars anyway. But whatever, its not really the topic. Could get its topic.