If you use Dual mode and enable Record Plus, you have a button to pick a preferred Output to use to record. If Single mode, Record Plus uses TV2.
I'm assuming you are defaulting to TV2. If you pick a Sat channel to record, the highest priority recording will go to TV2. A 2nd recording for the same time period will end up on TV1. If you pick an OTA channel to record, it will always say TV1 - TV2 can't select / view live OTA channels. My guess is you have an OTA antenna and those are the ones that show up as 1.
Which TUNER is much harder to answer since there isn't a direct correlation where TV2 always uses Tuner 2. If it is an OTA channel, it really is a Tuner that it is showing you, but they show the 1 for both OTA and TV1 output (causing confusion).