I found a cheap clamp on seat from Amazon for the rear rack because I was waiting for addmotor to release there’s but wanted to tow my girlfriend or kid around when ridding and it has worked great. It was under $20 too.
Take a look at this from addmotor to change the top speed in the advanced menu.
https://www.addmotor.com/faq/addmotor-lcd-display-features-and-operation-f0025.html#:~:text=Default%20max%20speed%20is%2032,(%2D)%2C%20confirm%20by%20pressing%20MODE.