Split Up's tapped-creature mode is the one to use. Cast it precombat on our turn, before we attack: their creatures that attacked or tapped for mana on their own turn, like Mossborn Hydra, Icetill Explorer and Llanowar Elves, are still tapped and get destroyed, while our untapped creatures survive. That is a strong swing against a deck that builds a wide board of landfall creatures. Smaug comes down a bit since it dies easily to Meltstrider's Resolve fights and Hard-Hitting Question from the opposing sideboard. We stay aggressive otherwise since Mono Green Landfall is a grindy ramp deck we want to race before Sapling Nursery or Ba Sing Se take over.