There is only one "flag" you can specify (besides 0): D3DX_UPDATE_NOVSYNC. The UpdateFrame function does either flipping or blitting AUTOMAGICALLY FOR YOU. (i.e. you don't tell it what method to use, it figures it out automatically based on the primary surface/back buffer features).
In the past, we had to worry about whether or not there were backbuffer(s), if we had backbuffers, then we had to flip, if not, then blit, etc. etc. The UpdateFrame supposedly takes care of this logic internally. Just call UpdateFrame - and it decides whether you need flipping/blitting/whatever...
Feel free to correct me if I am wrong (again, I am not new to DX, but I am new to D3DX)..
Chaster