Yes, transferred points may be banked. Banked points cannot be transferred.
Points may be transferred into the same Use Year (2017, 2018, etc.) in the other member's account. At this time a member could transfer points from their 2017 Use Year (regardless of the UY month) into another member's 2017 Use Year. Right now everyone is in their 2017 Use Year but beginning on February 1, the 2018 Use Years will begin and the transfer rules need to be considered when making/accepting a transfer. 2017 points must go into the other member's 2017 account and 2018 must go into 2018.
Members could even transfer points from two Use Years with one phone call as we can transfer from the current and next Use Year. Today members could transfer points from their 2017 and 2018 use Year to another member's account. The 2018 points could not be used until the start of that Use Year though, as transferred points cannot be borrowed.
Members with multiple memberships may transfer from one membership into the other. My understanding is that this would not count as one of your allowed transfers for your Use Year, but that policy is not in writing so it is up to MS whether to allow additional transfers from those memberships or not.
Enjoy!