Apparently, content blockers work on 32-bit CPUs, but Apple is restricting them on the store to 64-bit only. So you can go the BlockParty + EasyList route:
https://github.com/krishkumar/BlockParty
Another open-source iOS 9 content blocker here, using EasyList and EasyPrivacy: https://github.com/ArmandGrillet/Adios (I'm the guy behind this project).
As a data point, I just built/installed BlockParty on iPhone 5 and iPad Retina and see nothing but performance improvement. Many thanks again for the link!
