For the last 8 years I have used a rear hub motor, and never had any issues with the drive line.
Now that I have switched to a BBSHD I am experiencing chain stretch and wonder if there are some chains that are better than others.
If anyone has sorted through all the BS and has user experience...
On my BBSHD 52V system I use one of these and so far no problems.
https://www.amazon.com/gp/product/B0859J823G/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1