Tvheadend

1. Yes, I believe that recording always takes priority, and EPG scanning is at the bottom of the list. You also have shades of grey with recordings, though: have a look at the Automatic Recorder window and you'll see that each rule can have a separate priority. So exactly whether Live over-rides Unimportant but gives way to Normal or higher... ah, that's another story!

I think syslog shows the weight given to any activity, which would be a good place to start - see what a live subscription or a normal priority recording reports.

2. I don't believe there's any conflict checking, no. It would get really messy in a multi-tuner environment, especially if some channels were available on some tuners but not all (e.g. if you mixed DVB-S and -T tuners that had different but overlapping channel lists). I'd agree that it would be helpful, though.