I bought big laser cut CNC with 1m*1m dimensions and 7W LED laser, which can work in direct mode (15W lasers works only in impulse mode, and their average power is 5-7W)

For 100% power and 1000mm/sec head speed it gut about 1mm of plywood.

I think, that with 150-200mm/min speed it could cut 4mm plywood. But I need to do some experiments.