Qubes probably won't work, since it wants very specific hardware last I checked. Here's a techradar article that mentions a couple others. They're too new for me to have worked with, so I can't really recommend.

Qubes might be disqualified by the "low end hardware" requirement, it tends to perform better when you have lots of RAM. But it's hands down my favourite OS and it runs well on old hardware (as long as you have RAM).

Where Tails is like a hologram, poofing in and out of existence, Qubes is like a fortress with a lava moat around it. Very very different use paradigm.