Practice Room. Everyone is given the same exact plants at level 10 or Mastery level. This helps even the playing field, especially among new or lower-level players, but those with Mastery level plants will still have the advantage. Also, scores will still vary a lot based on luck: the timing and placement of enemies spawning (particularly Gargantuar, Mecha-Football, and Bug Bot Imp) relative to long plant cooldowns (they are longer than normal level 10s, sometimes 50% longer) make a huge difference.
My main tip is to keep Kiwibeasts alive, especially in column 7, by stalling with Squash and Solar Tomato (Plant Food on Kiwibeast works too), which helps keep zombies in the highest scoring zones and maximizes AOE damage. Gargantuar is the primary target, followed by Mecha-Football. Hunter Zombie needs to be countered as well because he'll freeze your plants: just make sure Squash is no more than 2 tiles away; Jalapeno will also work.
Note: Sometimes Kiwibeast and Squash get a free Plant Food effect (see the first Squash I plant at 0:11!), but I thought only Mastery level plants get this ability?
Lineup: Gold Bloom (10). Jalapeno (10), Kiwibeast (10), Power Lily (10), Solar Tomato (10), Squash (10)
Plants vs. Zombies 2: It's About Time Statistics For TheMaruMari
TheMaruMari presently has 379,740 views for Plants vs. Zombies 2: It's About Time across 1,808 videos, with the game making up over 4 days of published video on his channel. This is 48.70% of the total watchable video for Plants vs. Zombies 2: It's About Time on TheMaruMari's YouTube channel.