For riders, everything can be easily customized, grip tape, wheels, bearings, trucks, as long as it is on the board, and they put stickers on the board.
Electric skateboard/longboard users can do too.
The fastest and easiest way is to change the grip tape. Just choose your favorite grip tapes from eBay or Amazon, make sure it fits your board. Then tear the factory one off, put the new one on. In this step, the new grip tape usually not has the same shape and you need to cut it carefully. There is a trick to do that. Find a screwdriver, use its stick to press the rest grip tape along the deck, make it a 45-degree angle, you will get a white mark on it. Then use a sharp knife, cut the grip tape along the white mark.
Electric skateboards/longboards usually have high-quality wheels which are not good at reducing the vibration. So it is a good option to replace them with a soft one, your riding can be more comfortable. As for me, I prefer Orangatang wheels, it is awesome for riding.
Most of the electric skateboards/longboards have replaceable trucks, you can put your ideal one on to get a better riding experience. Just make sure the truck you got fits your board type. Skateboard trucks are different from longboard trucks. And different trucks have different features, you need to get the right one. For example P-type truck is very flexible, it is too hard to handle for newbies.
It is accepted that Bones Bearings are the best. It is a little bit expensive but worthy. If you are OK with the price, Bones bearings can improve the max mileage at some point.
Riders may not like the current board shape, for those who good with hands to move everything onto the new deck will be a good idea.
There is also a good solution for other people and normal skateboard/longboard riders. Skateboard/longboard kit will be what you need. It is specially designed for DIY, easy to install and dismount, and riders don’t have to make huge modifications to the deck.
Those ways will help you get an ideal customized electric skateboard/longboard. Also, don’t forget the stickers.