If you have USB debugging enabled, then you have ADB enable - it's one and the same thing. I run a custom ROM too; LineageOS or currently, crDroid. I've had Opus running with ADB enabled but I find it tends to be a bit flakey, so I turn ADB off. I don't use Explorer for file transfers so can't really comment whether it's any better than Opus. It maybe that Opus' implementation of MTP is slightly different to Microsoft's. In my experience, GP Software tend to have a better grip on the various protocols and implementations than Microsoft does anyway.