A bike seat isn't for safety like a car seat. It should be clear, but I will say it anyay, cars and bikes have different safety concerns.
- the most likely accident in a car would be a front end collision at some speed. On the bike the most likely accident with a child seat is a zero speed tip over.
- with a car seat, safely loading the child is done from a safe position. On your bike, you load the child while balancing the bike
- there is effectively zero chance of whiplash in a bike seat because the bike wheels, then bike, then you crumple, all before your neck. A car is much stronger.
You should mount the seat in a way where you can safely load and unload your child.
Pretty much all of the big brand E-bikes with child seats are similar. Especially if on the rear and not carrying two kids. Find one that's comfortable. I spent alot of time looking at them a few years ago.
The thought behind rear facing is that most car accidents are frontal collisions. Since the body is thrust in the direction of impact, the rear-facing seat means the spinal cord is more or less supported and doesn't shift much.
I don't think this would apply to bike collisions. Even if you're hit from the front, you're likely going to snap backward, to the side, etc.
The main things for safety really come down to the driver and maintenance. If you are a competent rider who pays attention to whats going on around you and you are riding a well maintained bike in safe areas, you and the kid will probably be okay. Though there is not guanrantee.
And please, please, please make sure that the child is in a helmet (and you should follow suite).