1) You actually can run it on both sides - see pelonx1st's setup.
2) You can do either - replace both mufflers with one or just replace the smaller muffler with a straight pipe or a MagnaPack. Look through my threads for the one about an exhaust and you'll learn plenty
"The Ultimate Driving Machine"
2006 BMW 750Li
- Style 128's with Michelin Pilot Super Sports, Magnaflow quad exhaust, ACS Roof Spoiler, ACS Aluminum Pedals, Umnitza LED License Plate Lights, Beltronics V995
1997 BMW 540i
- E39 M5 wheels, straight piped quad exhaust, CAI, Dinan performance chip, H&R springs
2002 Lexus LX470
- Window Tint (20%)
2012 Toyota Camry Hybrid LE
- Window Tint (30% front, 15% rear), LED interior lighting
2006 Mercedes-Benz S500
- AMG Sports Package - SOLD