There is no best ebike because most do what they are intended for or to do.
A 10k model isn't much better then a 1k model in the fact they will both work, the 10k will use different build material. You pay a high price for a lighter bike, brand name and stylish looking bike, the motor battery might be more innovative with less demand so prices are higher. Components will be lighter higher grade (means more expensive) but they will all work to a point for their intended market use.
Personally I would look for CS and how a company deals with issues over brand,price or locality.
You only have to see on here how many have had issues with Halfords and the Suntour bike system, though Halfords aren't admitting anything openly they are refunding, exchanging or upgrading bikes for others.
In the pedelecs world or esp on here the independent brands have high respect and regards for their bikes brand as they are knowledgeable about them and only selll their own design which they know back to front, though they tend to be the least fashionable against the big branded names.
Woosh, Wipser, Juicy, Oxygen are just four to mention.
The issue with ebikes is when something goes wrong buyers get frustrated and angry because someone hasn't done their job properly, a good company will sort out issues promptly or within a good time line and contacting them shouldn't be an issue.
In your case once you get the charger you be get good use of the bike and put the experience behind you, to get what you want badger is the only option and try every day so they don't just sit and rest on their laurel's.
Don't be fobbed off by the manager will call routine badger until you speak to one, keep on at them.
We know they are all busy with demand out stripping supply but that doesn't mean they should ignore current customer issues or complaints, don't be rude or blow your top, keep your head and be civil have all the facts and paper work details as you have. Going in to store might help but as they didn't originally supply the bike form the store may not or may be helpful, ask to see the manager to see if they can put wheels in motion.