Is there an addon that can tell me exactly what my speed is ingame?
What do you mean by speed? If it’s FPS or latency (people call it “ping” even though it really isn’t) then there is an option in settings to turn that on.
If you mean movement speed, there's an addon called ravSpeed
If you mean latency, there's an ingame setting to show that
If you mean FPS, there's also an ingame setting