What is the maximum size of CPU air cooler for a 135mm wide GPU at vertical installation with lan II-1X?

A CPU air cooler within 120mm wide would fit.

Type-C installation holes are too large on both sides to screw in.

Please screw the top one from the other side

How to sync ARGB of LANCOOL II to motherboard?

Push M button 7 times that comes to the 8th mode to sync the motherboard.

Can't find accessory box in LANCOOL II.

The accessory box is in the HDD tray

What's the clearance for a top mounted radiator of LANCOOL II?

The clearance for top radiator with fans is 55mm (max.)