They are the newest frame / kit on the market. Nivel has been working on some version of this kit for quite some time. As most people may not be aware that a lot of the stuff that they warehouse and sell is actually not their product. It may be badged their product but, if you figure out who manufacturers the unit you can order your own branded version.
A very large parts dealer has figured this out in one jurisdiction and is now ordering containers of tires, bodies, lift kits, chargers and you name it direct from the same manufacturers at massive discounts. Suffice to say you can purchase the same lift kits, with different stickers, for 30% discounts if you know how to identify the brand and where to shop.
Now this is not to say every product that Nivel sells isn't "unique" but, anything you see on one of these carts from this seller looks very familiar to many items in the Nivel catalog.
See:
https://szaoxiang.en.alibaba.com/
As well, if you want generic frames that are "TXT-like" you can get them here really cheap:
https://www.chinaalwayzev.com/
You can import if you are willing to buy units in volume.
ExCar has new units coming with 7kW motors and 80V @ 500A controllers I believe... (Search out NXT on Facebook they posted up some awesome stuff on the setup.)
The MadJax Storm X will sell well no doubt. The sales channel that Nivel has is massive. But, there is a fringe of dealers moving away and going factory direct themselves if they have enough capital. The cart market is going to splinter a lot now that people have figured out how to use the public import records from the USA to figure out where companies are buying stuff from.
Just search the various "bill of landing" databases that are all public record and you can figure out where the vast majority of "stuff" comes from. If is shipped in a container you can figure out where it came from and who sells the product. Contact the factory direct and they will sell you containers all day long too.