Hi Jerry,
before choosing any manufacturer, think first about your shop - what types of products you want and what level they will be. Then check the local competition. Think hard about something that will add value to that specific marketplace. Only then look for manufacturers. And select carefully - not only the manufacturer but also select only some products from the whole product line.
Check what the manufacturer tells you - confirm what they are saying because all will tell you that they are the best (it looks nice "on the paper," but in reality, it varies).
Look for support - I mean, if you have any problem with the product, if they can support you. You want somebody to answer your email or phone, and you need also support with technical help and spare parts. You want to work with somebody that keeps the word.
Also, look for good margins - you want to make money, not just sell.
Make sure to plan correctly - don't just think, "I will sell 200 ebikes Year 1, the margin is X, I will make Y". Do the real math.
There is much more to do, but don't overthink it. You need to move forward and take action. And don't waste so much time (like researching the manufacturers for two months is too much). It will make a big difference if you start doing business when the market is still in the early stage. Use the first active season to gain experience, then evaluate in the off-season (if you have it), and grow fast.
If you need some more advice, send me an email, and I can send you some helpful resources.