Well, I feel the very same way. I really don't know if there is any benefit from this. Actually it's just annoying to login and log out when doing different tasks. I'm sure they're able to link all of those accounts together very easily.

I agree. I'm sure Google has at least some idea of what's going on. I'll assume you're using pseudonyms and other falsified credentials in order to prevent Google from linking your information... but your phone's MAC address and IP indicate that the accounts are all being utilized regularly by the same device. The big question is whether or not Google's systems are sophisticated enough to distinguish one device with multiple users from a single user with multiple accounts. Because Google's algorithms are proprietary there's little chance we'll ever definitively know whether or not they're successfully seeing through your tactics (unless there's some sort of public privacy statement that I don't know about).

At this point I'd say the benefits are outweighed by the fact that your efforts could very well be pointless.

One limitation I know of is google can not change country of residence for merchant accounts, so make sense to keep different accounts atleast where it associated with card/bank.

I don't get it. What's wrong with profiling?