You already know this, Mike - for those that believe there's just "3" ways to play 'Two Shot Shoot Out' here's a few of the most popular variations - played by actual gamblers playing for real cash under strenuous conditions.
Here are rules variations that could be applied to 'Two Shot Shoot Out' 9 Ball.
1) Either all balls spot, or you agree to ONLY spot the ball before the "money ball"
2) Spot all balls behind the line (in the kitchen) or put them all down (except one before the money ball.
3) Re roll outs were only allowed playing "Two Fouls by the same person"
4) Re Roll Outs were NOT allowed (without giving up ball-in-hand) playing "any two fouls"
5) Alternate breaks (not our favorite way to play, but chosen by some)
6) Winner breaks (most common)
7) Loser breaks (least common)
8) Ball frozen on the rail would make the rail "dead" and you have to go
another rail for a legal hit....this could be cue ball or object ball.
9) Frozen balls don't "kill" rail
10) Three fouls are loss of game (rare, but did come up in two shot shoot out)
11) No Three Foul Rule - occasionally this could result in a stale mate if a ball was wedged in the corner by another ball.....balls were re racked and broken again.
12) "Races" or "Ahead Sets" were common, races were the first one to a
given number (11) and ahead sets were first one to get X games ahead of opponent.
We also played a lot "by the game" - this was back when there was more "heart".
We always played the Ball-in-Hand anywhere on the table exactly like "one-foul-ball-in-hand".....although there were people that played "behind the line" on any foul - they were a special group we called........better not divulge their slang names.
These are most of the main rules variations, although there are a few more. They're not complicated, we actually had a "standard" set of rules for the professional gamblers in the country, we played virtually the same way although it paid to know how the different rules variations effected the "matching up" process.
I actually was schooled on this as well in the prestigious college I attended on the road called "Pool School".

'The Game was our Teacher'