Can I run SRAM double tap road shifters with MTB (X5, X7) derailleurs and cassette/chainrings? I want to get lower bottom gears than achieved with a 50-34 chainset and 34-11 cassette
Back: All the SRAM rear derailleurs which have "exact actuation" (1:1 actuation ratio) should work. This includes the X5 and X7. You can run a "mountain" or "road" cassette, its pretty much just marketing that differentiates them provided the derailleur has enough capacity to use it.
Front: On the other hand, in the front, the cable pulls are different, so you will need the road SRAM FD. The FD should be matched to the type of front crankset (double or triple) and the spec sheet will tell you the constraints on the chainring sizes which the derailleur can shift.