The motor just translates what's available from the controller into motion.
If the controller can't provide more power, a more powerful motor doesn't do much, or anything, other than potentially heating up less for the same load vs a smaller one.
A bigger controller can only provide the power if the battery is able to provide it, so you also have to have a battery capable of the power you want the system to have.
Whether any of that power actually gets used depends on the load you put on the system, so if your terrain, speed, etc don't need that much power, it won't change much to have bigger motors, controllers, and batteries, other than to empty your wallet faster.
You can use calculators and simulators like those at ebikes.ca in the tools section to find out how much power it should take to do the job you need the system to do for you under your specific riding conditions.
Also, a more powerful system uses the battery capacity faster, so you then need a bigger battery to provide all that power for the range you need. The bigger battery is heavier, so it takes more power to move it; at some point you get to a scooter the size of a car that cant' even move under it's own power anymore.
