Is there a way to see all the hot/popular threads? I can't seem to see a possible way, in Advanced Search you can search by number of posts or views but I must enter a search term, which I don't want to do.

There's a widget called "Popular Content" available, which would show you the hot (popular) widgets

Not sure if this is what you are looking for. There is a 'Popular Now' Block you can enable to show up on right on Board Homepage. You can set parameters and when enabled the most active Topics shows up there.

AdminCP>Community>Settings>Forum Settings>Topic Settings