On most domestic routes, they aren't super strict IME, but they often don't want wheeled luggage in the cabin unless it weighs in at less than ~7kg (e.g. this was the case on my PVG-NRT flight last week). This makes for much faster boarding and deplaning, and is a fairly common policy in Asia.

ETA: There's little downside to trying to carry on a larger bag. If you get denied, it will almost certainly happen at the check-in counter (i.e not the gate) and they'll simply tag it for you on the spot.