There are many ways to look at L2 but yes, they can put up huge blocks (walls). Another is to put up a 100 placeholder but have underlying orders that keep the 100 in place until those orders are filled.
A good way to watch L2 is to watch the bid/ask spread. If there is a gap between them, then they have playing room to manipulate price more. A rising bid on a tight spread is a good sign. If the bid starts dropping, the price usually follows soon after.
And yes, you get to know which tricks each MM uses so you can react accordingly depending on who shows up at the table but that takes time and experience.
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