fwiw - I have a friend who rides an Ansbern Boost - with Bafang and Rockshox components -
He ordered from Alibaba, under $2,500 USD I think
Circling back to your TLDR - Buy a Specialized, Trek or Giant from the your favorite LBS. Demo the different models, buy one and ride the bikes much as you can during the warranty period - if you still like it after that, you add it to your quiver as a backup bike ha ha
I think Shimano may be back in the game - I rode the EP801 installed on a Yeti at Outerbike - and it was every bit as good as Bosch and Brose. No 'rattle' could be detected. Plus you have auto shift to play with etc.
No, but I remember the guy saying something about using the etube app for shift tuning. I discovered that I could do a 'quick burst of cadence' to encourage the (SRAM) system to shift - but that's my brain and not the computer doing the shifting, right?
I also tested the Shimano auto shift, same day, same test lap - yes it was slow shifting on test lap etc.
I liked the Shimano display - gear selection, rider power meter - plus easier to see at a quick glance.
I was lucky enough to demo the 'automatic transmission' and long story short, it did not shift fast enough for me. Most riders I talked to said the same thing. I adjusted the +3 to -3 settings but I could not get it better. No doubt a good demo from a salesman would have helped . . .
About 10 yrs ago, we visited Santa Cruz headquarters (in Santa Cruz) and we rode demo bikes etc. If they still offer demos, you can ride out of town or you can shuttle to the top and ride back to town as I remember. I am not sure if E-riding is accepted there though?