Hope you are doing fine.
1) I have decided to make my 1st product, a Car Charger, with full metal body, and Qualcomm quick charger 3.0 feature supported?
>>>First on car charger it is restricted product on Amazon. You require safety test report and other things. So we don’t suggest you go with a car charger. Products that are listed before that is 2-3 months back are shown on Amazon.
Try to find other products that are not restricted and that does not require any safety report because it can be complex process.
Let me answer your other queries.
2) I would like to know what is OEM number and how to get it, if I decide to get one?
>>>To get exact OEM you have to talk to manufacturer to know their OEM. Usually they write higher OEM numbers in Alibaba listing so it’s always good to talk to them to get exact OEM numbers. As you mentioned some of manufacturer charge additional to printing your brand on their product. In this case they don’t provide OEM numbers they provide additional charges.
Let me know if you have selected other products and will help you to finalize one.