I'll answer what I know:
There is no real benefit to gold connectors (just marketing.)
Once a DTV receiver locks on a signal, the picture quality is fixed. You will get all the resolution a station provides. Most main channels will be in HD (there will still be 4:3 programs, though.) Most sub-channels will be standard definition. To see what your market offers, go to
RabbitEars, click on the market, then explore the channels.