Sorry not an expert on this, but at least the main question has been answered.
For your photo's you could easily transfer them to a PC and then to the new phone (If you need to) or just put them in OneDrive, I am sure the messages are linked to your account, but maybe the migrate process can bypass this, again with data it would depend on if it was account linked or standard files, if you mean files again you could copy to PC.
But as I said, I haven't done this and as you already have a live phone, it is wise to look before you leap.
How much data is on the 950, would it be a pain to start over, or if you got the photo's sorted a pain to let the 920's data go. I am sure someone else has been through this and will be along at some time to help.
PS You can call me Bob, the VFR bit is a Honda motorcycle I own, I think they are called Interceptors in the US.