Checking the [hide Blizzard raid frames] option in the general tab causes the quest log frame to become huge and change location. Tested with clean SavedVariables and no other addons active; happens whether actually in a raid or ungrouped.

Which Grid2 version ? Issues with that option were fixed in 2.0.61-beta

Changing the "hide blizzard raid frames" does not deactivate the (5man) party frame.

The party frames issue should be fixed in version 2.0.62-beta