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Yes, most of the features can be used without connecting to SteemConnect, but for the few ones that need posting permissions, it is handled through SteemConnect. We never access your private keys and this since v2.0

it is handled through SteemConnect
excellent.
that's what I wanted to know.
I never access anything that doesn't use SteemConnect.

Sure, that would be too risky.
To access the features requiring the posting permission, you can login to SC either via the SteemPlus popup or via the SteemPlus button next to your userpic.