Welcome and looks like a fun build.
a couple suggestions - i would personally start with the ESC and voltage (# Series) of the battery you are going to use? I’d usually recommend starting with two 3s batteries in series for 6s. This gives you a lot of flexibility as most ESC’s are capable of 6s voltage. And if you get a VESC or similar you can add a 3rd 3s battery for 9s later, or a 4th for 12s if your kv of your motor is low enough to avoid 60k ERPM (where the DRV chip can/likely will have issues).
SO - ESC you want to use?
Where are you riding - hills or flats?
What kind of riding? Cruising, commuting, racing?
How heavy are you?
What’s your realistic budget?
Speed (your goal is 35kmh?) is just a factor of wheel size, motor kv, # Series/voltage of battery, and gearing (motor/wheel).
So an example setup to hit your target speed:
83mm wheels - 190kv - 8s - 15/36 (one of the most common - the kit enertion sells uses this too) = 35kmh
But at 8s you will need an expensive RC ESC, or VESC, or similar.
Same setup just swap in 245kv motor, and 6s battery = 35kmh again.
I’d grab one of the calculators and play with the settings to see what gets you where you want to go speed wise. If hills or acceleration are your goal - i might even gear down further with a smaller motor gear (no smaller than 13t - especially on 9mm wide belts or it will skip), or go larger on the wheel gear 36->40t, or larger if you want to print some from thingiverse.
range - there are some rough ways to estimate your range. Best is to use Watt Hours (Wh). Take your battery pack voltage (6s @3.7v nominal = 22.2v) x Amp Hours (convert from mAh) = Wh. So an example is some of the zippy or similar 3s (2 in series) 5000mAh (5Ah) 20c packs. So 22.2v (6s) x 5Ah = 111Wh.
You should expect (with moderate riding and weight) to get about 1km per 10Wh. So 111Wh = 11km. If you want more, you need a higher Ah pack, or more voltage (more batteries in series for 9s as example). a 9s pack (3.7v x 9) = 33.3v x 5Ah = 166Wh = 16km!
A lot to take in - give us some of the above detail and we’ll help you figure it out!
HTH - GL!
