Not all 650+ will take 29er wheels, or at least decent wide tyres, so I’d try before you buy..
again im a fan of lots of travel is good on e-bikes (mine is 170mm), but a (e-biker) friend did hire a ST powerfly & thoroughly enjoyed its more nippy/responsive nature. Though he did go onto buy a LT giant (knows the distributor, so no reflection on the trek), as it simply makes more sense.
ive spent the last 6 months bashing mine down every trail I can find, & I can find a lot when you have a motor to help. I don’t do big drops, but I’m a big(ish) lad & the electric’s have been fault-less due to ‘shake rattle & roll’ of general DH mtb-ing.
They are more inherently likely to break due to some-thing electronic, my first one was broken out if the box, so I will be aiming to buy my next one from a local specialist (not just an lbs, but a shop embracing them). That said I bought mine simply because it was an online bargain