A bit late to this thread but …
Also I’m not reading through the whole thread again so if something’s already been said, apologies.
The main problem with plus sized tyres is that in order to keep the weight down (low weight being one of the must haves that we’ve been told we need in bike tyres) then something’s got to give, the choice is between the sidewalls and the tread. As far as the manufacturer is concerned the sidewall is preferred as it enhances that soft plush feeling they can use to sell the tyres.
I’ve a set of 650b+ wheels running WTB Bridger on the front and WTB Trailblazer on the rear. (This is on a Solaris) I’ve seen comments on here and elsewhere and been told by riders that having the TB on the front wasn’t a good idea so I’m not sure why Cotic still run with it in their Plus package for the Solaris. Having done some measurements the sidewalls on the TB are wider than the tread! I’ve done around 800Km with the Plus tyres and still going fine.
I’ve just got back from Iceland and the tyres stood up fine even though there were some rocks I thought were a little on the razor side of sharp. A lot’s down to chance really which is the same as with any tyre.