There's good hiking in Indian Heaven. It's where I've gone for my last few and I plan on exploring it more in 2023. It's becoming one of my favorite places.

The big one was in 1980, but there had been active dome building up until 2008 with the occasional smaller eruption. I recall seeing a few steam plumes from Vancouver in 2004.

https://en.wikipedia.org/wiki/Mount_St._Helens#2004_to_2008_activity

Adams is the largest by volume - though not as tall as Rainier, it is made of a greater amount of rock overall.

Of the two, Rainier is more active and poses a much bigger threat to population centers.