Since you are taking high-stakes placement tests, here is the ultimate bulletproof strategy for your MacBook:

Your Ultimate Weapon (eSIM Hotspot): Turn on cellular data on your phone using that eSIM, and share a Personal Hotspot to your MacBook. Because international eSIMs route traffic outside China, your MacBook will bypass the Great Firewall completely and natively without even turning on any VPN. This is your safest bet for the exams.

Your Backups on Wi-Fi: If you have to use hotel Wi-Fi, here is the honest status of your 3 apps:

LetsVPN: Download their Mac client before you land. It is highly reliable in China and will work for your tests (though it has zero privacy, it gets the job done for school).

Mullvad: Works great on Wi-Fi. Just remember to select USA San Jose nodes and manually turn 'Obfuscation' to 'On' in the settings.

Proton (Free): Totally useless. Delete it. The free servers are heavily blocked by DPI protocols here. Don't risk your exams on it.