Turning off the social networking will definitely help battery life. You can also use the "smart" rather than "performance" battery setting. I don't find the phone laggy, but as with most devices, the less that's running, the faster it will be.
You can manage your MOTOBLUR account using your PC and you could probably request it be deleted. But if you aren't going to enter any info for syncing to social networking or contacts or anything, then it's pretty much an empty account anyway with just your name and email address.