* China spying will steal your data and identity so the safety of your money and assets will be at risk. Your photos may be sold, your credit cards may be stolen, etc.
* Five Eyes spying will hurt you if you're non-normative. Say you're a casual drug user or perform low scale criminality. Or say you're doing a thing that's legal now but illegal later.
Presumably there's the idea that China could blackmail you but I have a hard time believing anyone would go for that over just letting their naked pics on the Internet.
So the Five Eyes spying is probably harmless to someone totally normative. The China spying is probably harmful to them.
For the non-normative, dark-web peer to peer Bitcoin user who is buying LSD, the China spying is probably better.
A friend of mine was on the team that investigated the Twitter 'breach' that got those Saudi activists disappeared. Through personal experience I find it easy to believe that technique would have been more effective on a Chinese company but since I cannot communicate that experience and since you don't share it, I can accept that our views must diverge.
And yes, I'm also a drug-using dark-web crypto user. Had to keep that one quiet from the investigator friend, eh?
If you are really serious and you won't flash a new ROM then you will need to filter the traffic after it leaves the phone as you cannot trust the phone or its apps. IMO the only way to do this is to use a VPN to connect to a device that runs a proper firewall. It could either be a Raspberry Pi you carry around (bit too geeky for me) or a server somewhere you trust. I connect to a pfsense machine at home via VPN and filter traffic with pfblockerng. You can block on geography if you want.
My girlfriend's iPhone is just as bad as my OnePlus..