If your device is out of your sight, then yeah, you should probably assume it’s compromised.
Of course, that’s hardly JUST China doing funky removed with your devices, but depending where you’re calling home, odds are customs/immigration when you head home will try to do the exact same thing, too.
And the answer to everything is yes, always use a VPN if you don’t trust the network and you should never trust the network.
For sure, just wanted to mention that it’s not just the China side of the trip you need to be vigilant about.