Sat cables should be connected to LNB in or LNB A, LNB B
If your cables are set up correctly the recording etc will work as long as both tuners are set up to the satellites you want to use.
Normally you record one channel and watch another.its possible to record more than 2 channels and watch a third channel but you would have to be on the same transponder.
For example, it's possible to record two movie channels and watch a third some of them are on the same transponders.
Only way to find out is try out for your self on different channels, you will k ow when you run out of things to watch because the channel list will go grey.