HTC One M7 :: Contacts Sync Between Android And Gmail

I moved from iPhone to HTC One (on VZW) recently and I am having a hard time figuring out the syncing process on Android phones, esp HTC One I have. I have a gmail account and a lot of contacts are there, but there are some that were only on my iPhone so I imported all my iPhone ones to the HTC One.

I consider myself a power user. Please do not refer to older apps (like Contacts, its really People app now in JB). Also, I have lost about 60 contacts recently while trying to figure out the process.

I think it would be useful if I ask few specific questions:

1. Are gmail contacts the master contacts for syncing purposes? If yes, what is the role of Google+?

2. If I'd like all my contacts to be always backed up and in sync with Gmail contacts, does it really make sense to have local phone contact? Somebody I met recently showed me that he adds all his contacts directly to Google from the phone (HTC One), so I was wondering if keeping local phone contact is really necessary. Mention any scenarios in which local phone contacts would be appropriate.

3. How does the relationship between phone contact and my google contact (gmail, that is) work in terms of addition, update and delete? When I erased all my contacts on phone, it ended up erasing my contacts from gmail when I tried to sync contacts.

4. In HTC One People app, when you add a contact, it defaults to "Phone". Is there a way to change that default to "Google account"? I saw on someone's phone and they could not explain how that was configured.