1) IMO. 16 or 20. It enables the 4 POD scheduling of either 4 per POD or 5 per POD. That is the most flexible scheduling.
2) The Big XII is totally dependent on what Texas wants. If Texas wants to keep the Big XII together, the Big XII will stay together. If Texas wants to do something different, there is no Big XII. Its footprint is too small for a network, and Texas has their own. Those other 9 schools are at the beck and call of Texas. That's not anything I want my school do. Texas is now being shown up by Texas A&M. So I think Texas could get ancy, and boom, no more Big XII at least as a P5.
3)The SEC could target West Virginia, Texas, Oklahoma, Oklahoma State, Texas Tech, Kansas, Kansas State. The B1G wants contiguous and AAU. That's Iowa State, Kansas, Vanderbilt, Missouri, Virginia, etc. But UVA isn't coming. Two of those others might, and UConn is interested. The ACC would probably target schools from the AAC including UConn, Cincinnati, Tulane, South Florida, Central Florida, Temple, or from the Big XII in West Virginia, Texas, Texas Tech, Baylor, etc.
The ACC has to determine where it wants to end up 16 or 20. If it is 16, I say add UConn and offer Navy or BYU as football only until we sort out what Notre Dame will end up doing. If it is 20 then there are a lot of other possibilities.