The trend in recent years has been to run a "lower pressure" position in the bore, meaning a longer than standard gas length, hence the rise of mid-length, intermediate Nov & KAC gas systems. However, these are only an advantage if used with a "dumb" gas block, and then leave the user vulnerable to lack of gas flow with lighter loads, or faster, lighter bullets (shorter dwell time. Alternatively, by running an AGB on a shorter gas system, aka a pistol length instead of a carbine length on a 10.5" barrel, a carbine on a 16" barrel instead of a mid/inter, or a midlength instead of a rifle on an 18" barrel, you can throttle the gas flow to a lower impulse. No, you shouldn't be running a carbine length system on a 20" barrel, or a pistol length on a 16", but for a couple barrel lengths where there's a decision to be made, I ALWAYS go short and add an AGB, instead of running the risk of insufficient flow on a longer system.

What failure did he have with the Remington BCG? I'd be interested to hear. BCG failures are exceedingly rare. Out of spec manufacturing is far more common than wear-and-tear failures.

Semiauto BCG's will not wear out any faster than a Full-Auto design, anyone claiming such is simply lying to you. The only difference is the cut at the tail of the BCG. There is no difference in durability when used in semiauto fire, and frankly, I'm not prone to believe there's a significant difference if used for simulated full auto fire (the FA bolt typically engages the select fire mechanism, so an SA bolt couldn't be used for true FA fire, only for simulated FA, like a binary trigger, bump stock, or trigger crank). FA bolt carriers ARE popular among SA shooters and AR builders, since they have a bit of extra weight compared to the SA bolts, which slows down the recoil impulse and reduces some of the action battering. Adding an extra weight buffer will accomplish the same end. FA BCG's are REALLY popular because mil-spec mall ninjas all over the internet say they should be popular, misleading folks into thinking mil-spec and FA actually mean something important in terms of rifle function and durability in SA civilian AR's.

There's no "wobble" caused by over-spinning the bullet. The only negative consequences of excessive rate of twist are 1) bullet stress, where the bullet may tear itself apart as it leaves the muzzle, and 2) extra bore drag, where the bullet can't be pushed as fast as it otherwise could be with a slower twist.

Largely, there is unstable and stable, and no such thing as "over stable". The farther you get down range, the more spin you need. Poor quality bullets are going to exhibit yaw, exaggerated down range, and those imbalances will also be exaggerated by insufficient stabilizing spin. Over-stabilization is bad science.