With exception of YMY, Forest is one of the easiest terrains because of the favored Ninja and the generally long tracks. The lack of Farm is generally overshadowed by how well Ninja can carry the early game and deal massive MOAB damage when spamming Bloonjitsus (including to DDTs with an Monkey Intelligence Bureau) and stunning Bloons with Flash Bomb.
On YMY, the bends near the start are useful for area-based towers to cover, such as Bomb Shooters, while the main cleanup should be nearer the back and is recommended to be a Spike Factory with at least Faster Production.