If you want to prevent an attacker from using your main account (and therefore having access to all your accounts if they rely on the main account for password recovering), then all you have to do is probably two things:
- Block your phone number. It depends on your provider, but when your SIM gets stolen they should be able to block the number pretty quickly.
- Go to Google and try to disconnect your account from all devices, and then change your password.
As for the "lock and erase" feature, I'm not sure how much it can be relied on. I read that localization (GPS) has to be turned on for it to work. Also, an internet connection is needed of course. So if the thief just turns off the data connection, or pulls out the SIM card, or maybe just turns off the GPS, etc., you might not be able to "lock and erase" the device. Or you might not be able to do it quickly enough, anyway.
So, if you want to prevent an attacker from also reading your email, accessing your documents, etc. (all things that are saved on your phone), plus also protecting from attackers that steal your phone from your hands (so it's unlocked), then I'm afraid there's no way to do it, unless you accept to mitigate the risk some ways, for example:
- Only associate your device with a Google account that you only use for the phone and nothing else (a kind of "dummy" account)
- Don't send and receive any email from other accounts
- If you want to read the mail from some accounts, set up a forward copy to be sent to your "dummy" Google account of your device, and whenever you read an email you must remember to delete it
Basically you will need to accept that you can't use such a phone easily for work, unless maybe you are ok with only reading the emails and then immediately delete them. But you won't be able to do many more things, as it will basically be like running around in public with your office in your hands, waiting for a thief to steal it.