Lots of worthy kits out there. My suggestion is don't overthink the process and listen to the people who actually have ebikes rather than people who openly dislike the idea.
Anything you put on your bike will add weight. The bulk of weight will be in the battery. The motors and controllers are all roughly the same weight. Keep in mind battery tech is still in the bronze age. Even the best batteries require a fair amount of weight to yield a usable range. That is why electric pickup trucks use batteries that weigh more than a Honda Civic.
Don't be scared off by weight on an ebike. Touring and backpacking bikes routinely exceed 50 pounds. So even with a depleted battery a heavy bike can be ridden. Keep in mind a rider gets plenty of warning before a battery runs out of juice. One can conserve range by slowing down and using less electric boost to get home
IMO DIY kits on older bikes are a much better option than "factory" bikes. The idea older frames weren't designed for the added power is bit of a fallacy. High power hub motors may require a torque arm to keep from rounding out fork drop outs. But other than that ebikes use the same components that bikes have been using for 100 years.
As for factory stuff, man, so many options. But way too many of those seem to be designed toward casual riders without any regards to weight.
Like 2old I put a mid drive on an 80's vintage Cannondale aluminum mountain bike. 3 years of zero, I mean zero, issues. I built one just for the experience. Shortly after I went through a couple of back to back surgeries. The ebike was a God send during those recoveries allowing me to ride without worry. Turn down the boost to push the recovery, but still have power to get home if I bonked or started hurting.