I used the following for my water bottle setup and am happy with it:

Cascade Manufacturing Bottle Cage Mounting Bracket for Rad Power Bike
https://amzn.to/3f0OeDK

Lumintrail Adjustable Bike Lightweight Aluminum Alloy Water Bottle Cage Holder
https://amzn.to/3tEdQKw

Camelback Podium Water Bottle  21oz (8 1/4" tall)
https://amzn.to/3vXsDCn

The Cloud 9 Cruiser seat is not a smooth swap on the RadRover due to the fact that the mounting hardware on the C9 is slightly wider than receiving hardware on the RR. You have to use a vise or some other method to narrow the seat mounting hardware slightly to fit. The C9 seat is really meant to mount straight to the post but can’t do it on the stock RR seat post. You can make it work on the RR but you’re gonna have to do some work. Know what you’re getting into!

Few different types of bike locks....D-Lock, chain, cable, folding. I am leaning towards folding for ease of transport. Any recommendations?