I know zilch about Liriope, but some like sun and others like shade. Plant straight up and make sure roots are pulled apart a bit....and not coiled as they come out of container. Put a 20-10-10 lawn fertilizer tablet at bottom of hole. Do you like daylilly? They have great roots for holding soil together. No need to remove mulch. Not sure about Pampas grass for your area. Either sterile or free seeding. You might ask.