They use a resistant oligosaccharide as their fiber. I think they’re fine in a pinch, but I wouldn’t depend on them as a staple in your diet.

They actually got sued for mislabeling their products. People tend to handle sugar alcohols and resistant saccharides differently. If you plateau a bit, that’d be the first thing to avoid.

I haven’t found any good ones. If you want quick easy protein beef jerky, cheeses, and nuts are likely your best bet. Oikos triple zero yogurt is a good choice, as is skyr.