those are agile tuners, so the sat in #2 can be feed your tv 1, or sat in #2 can be feeding tv2, etc. all of the decoding, compression and recording happens within the rcvr before it gets sent to the ouputs for tv 1 or 2. it wont matter what tuner you record on. so yes, "tv2" can record hd, and it can do it while tv1 records hd too :up
Look at it this way: The tuners and the outputs are entirely independent of each other. The two satellite tuners and the OTA tuner can all record HD. So you could record 3 HD programs at the same time. Then watch in HD on the TV connected to the TV1 output, and in SD on the TV2 output.
Many HD channels have an SD counterpart. I'd suggest selecting the channel carefully, and ensuring you don't have your system set up to revert to recording in HD when available anyway. Seems counterproductive though. If you need more space, get one or more external hard drives and move programs to them.
If space is the problem, you may be better served to connect a External Hard Drive. True sd uses a lot less space, but it is never going to look as good as HD.