#1. Most of those points are not true, but some aren't so much false as they are opinion or preference. Definitely not gospel in any sense.
#2. The only consideration you really need to make, is in terms of what systems are reliable and proven, especially in regards to the recoil system. Gas systems aren't terribly tricky as long as your gas port is the correct size and you have the correct gas tube length.
#3. Unless you buy a barrel with an oversized gas port, or are running a suppressor, you're better served running a fixed gas block. I prefer the clamp-on type myself.