Tp link Archer c7 with openwrt

I’d recommend setting up the router so that “dns requests” are always forwarded to your pihole so that at least hardcoded dns servers are caught. Depends on the router how this can be done (if at all).

This. If it’s completely overkill it’s likely going to use a lot of power and you’ll pay for compute power that you don’t actually need.

I’d stick with the pi4. I had 12 or so services running on it without problems.

If you are willing to DIY you could create your own.

https://kno.wled.ge/advanced/audio-reactive/

I used to let root start the backup job

Perfect! I rely on it heavily for my remote backups.

Did you disable secure dns in your browser?