1) What's the deal with metal and gear? The helpfile talks about them doing well without clothing, and I've heard they suffer from wearing metal or using metal weapons. How does this work?

A: One piece of metal kills your onslaught ambush bonus. More will make other skills (camo, creep, etc) fail. As far as weaknesses of savage go, no metal is really the only one. Savages do have a few skills that key off of empty slots, but overall I'd say you are better off fully clothed unless you don't have non-metal options.

2) What options do they have to lag their victims?

A: Bearcharge if the build gets it and Savage blow. With size advantage, Bearcharge is more lag, but can be stopped by bash protection (protective shield, etc). I don't think there is a a counter to Savage blow, and Savage blow does ok damage as well and has a small chance to knock out your opponent.

3) Any other big considerations or downsides to take into account with trying a cloud giant savage forester (likely Villager) ranger?

I wouldn't go village because then you can't cast protection from metal which I would say is one of the biggest upsides of a savage ranger compared to survivalist. Also can't use entangle, call lightning, or imbue staffs.

To maximize the build I would go outlander since you will be wearing natural gear, you should be able to strengthen all of it and you will be more likely to have druid friends to transmute metal to wood for you.