RE: 70mm F16 EDF Speed
Electric planes are a balancing act.
To increase performance you might want to opt for a LARGER higher KV motor.
It needs to be larger to handle the extra current draw. If you simply replace the motor with a higher KV unit of the same size, the motor will likely overheat to the point of ruining the magnets.
A larger motor adds weight, and draws more current, so you may also need to deal with the ESC and battery too, upgrading both of these will add more weight.
More weight equals poorer performance, so your end result might be that the plane will handle exactly as before... but be prone to stalling more easily!
Been there, done that myself!
In your shoes I'd opt for a 5C battery knowing that I MAY ruin the motor and ESC if not the BEC too.
But your best bet with a known fairly well working plane, is to REDUCE it's weight as much as possible.
Anything you could do to shave a few ounces will improve performance as dramatically as a new power setup....
Also check your intakes and exhaust. Sand and smooth them as much as possible to improve airflow.
Been there, done that too!