trash,
As much as I hate saying this since I am an avid Avast user, but you can run Norton and use Avast as a "backup" if you remove the resident scanner module.
What Technical means is that both cannot run resident at the same time.
However to be fair, Norton can run as the primary AV with Avast in the background dormant.
I will say that if you only use Avast as a manual scanner, you are losing some of the best benefits of the software.
If you wish a recommendation, then take Connie's. She is right on the money!
Good luck.