The radio/media are equally as bad as the rag/media at not getting the true facts before reporting, again the 15.5mph limit is fake news and you are as bad as the press by not doing your homework.
Gov't have stated 12.5mph is the limit...
Already a thread started a couple of months ago.
https://www.pedelecs.co.uk/forum/threads/e-scooter-trials.37568/#post-565513
Trial scooters are the only legal ones allowed which will have insurance and speed limitation.
2 x gives a 11.3 degree spoke /nipple angle which is pretty good , 238mm is good for the spoke calc I used, 1 x is 6.4 degree angle.
14g is all I use, for spokes I use 'Spokesfromryan' and use Sapim Strongs a 2mm/14g spoke with a 2.3mm threaded end.
The buck converter isn't needed you can by stvzo lights with internal step down voltage and integral horn they then simply run off the battery via a switch, the the Tongsheng uses a splitter light /gear change sensor splitter cable whether this can power the lights enough I don't know.
ERD is stated as 578mm for the rim.
You will have to measure the spoke hole diameter across the hub.
The spoke calc will give a spoke entry angle so if it need be adjust the cross pattern and recalculate.
CST will likely need some dish but you can do that in the dropouts easily.
Spoke/nipple...
If the rim ERD isn't specified by the seller two ways to get it.
1. Measure the rim inside in a couple of places to get the correct diameter and add 4 or 5mm for the rim wall thickness.
2. Cut down two old spokes the same length and screwed the nipple fully on, insert them in to the rim...
That's because they are box sellers and know nothing about ebikes and just sell the Chinese mid drive crap. They think Bosch etc, are built in Germany but all are Far East produced.
You need to input the details in to a spoke calculator.
https://www.wheelpro.co.uk/spokecalc/
You will need to know the rim ERD (effective rim diameter) this is the seat position of the nipple to the opposite side, the hubs spoke hole effective diameter.
For the lacing you will have to opt for...
It's a hub motor axle they are fixed in length, you can't adjust them like a ball and cone QR type.
If you can find someone who can carry out fine welding then it might be poss to tack the hitch to the outside of the nut ?