After getting our Rad Wagon last year we made only a few modifications such as adding battery powered colored lights, modifying the running boards for a bike trailer and using bungee cords to affix a rear basket. There are generally a few popular modifications I see people make initially, usually adding a more comfortable seat (
like the cloud 9 seats) and if they're really serious about comfort a suspension seatpost (
like this one from Suntour).
I'd argue one of the most important modifications to make to your ebike initially have to do with safety. Beyond gear to be seen (we wear safety vests), more lights are always a good add-on but mirrors are also important. Many mirrors will fit your Rad, but the
Mirrycle Bicycle Mirror is one of the most popular.
It can be purchased for around $10 and is extremely easy to install as I recently found out. A few pieces to screw together, pop off the end cap on your bike, put the mirror into the handlebar and finally tighten. It comes with all of the tools you need in the box. There are probably some other options which look a bit sleeker but we're really happy with the Mirrycle. See below for the pictures of it installed.
Mirrycle Bicycle Mirror on AmazonOther accessories including more mirror options on my Rad Power Bikes accessories page:
https://www.radowners.com/index.php/topic,104.0.htmlPlease note you need to register for a forum account to see the images.