Personally I watched lots of conversion vids on YT.
I was interested in the Swytch conversion as it seemed a well engineered kit that didn't cost too much so long as you join the waiting list. However I'm a fairly fit cyclist and wanted something to help cruising above 20 mph for my 20 mile each way commute. Only way was an "off road" conversion from DillengerUK.
Ended up doing my own conversion to a road bike and quickly learned you actually need a gravel bike (or hybrid) with 30+ profile tyres to resist the extra mass at speed to avoid broken spokes etc.
I highly recommend sticking to a mid-mount conversion kit as they tend to work best overall. My motor is rear wheel mounted as I like to take the motor/battery off at weekends for maximum exercise.
The DillengerUK Bafang conversion kits are a good place to start your comparisons. They have good customer support and will answer your questions though they are in Oz so there is a time difference.