For the remote I would suggest,
Benchweel, or the GT2B.
Belt wise I would wait until you get the motor mount and pulleys, that way you can measure out a relatively accurate center distance and the buy belts accordingly, otherwise you’ll be guessing, I made that mistake and gotta spend another $25. No biggy.
You can either go with the farthest distance from the center of the axle side to the approximate location of the motor shaft and call that your center distance. Or you can make a CAD model of the mount and find the distances.
My advice would be to get the mounts and motor, mock it up, then measure.
https://sdp-si.com/eStore/CenterDistanceDesigner
That’s a good calculator that I have used before. From there. You can get the belt length and number of teeth based on the three key information you put into the calculator.
1.# of teeth on motor pulley
2.# of teeth on wheel pulley
And
3.center distance
Then just Google a belt like that.
With the Torqueboards motor mount which is 45mm center to center 15/36T pullies you will need 265mm belt, on the same mount and 15/40T you will need 280mm belt, on 15/33T 255mm would be perfect