If you're a purist, then the top three choices would be:
1) No playoffs. Regular-season winner is the champ. But that's kinda boring, especially if there's no pennant race.
2) One of the four-team playoff (Shaughnessy) scenarios.
3) Split-season, where the winners of the 1st & 2nd halves play for the marbles.
Obviously, you could just have #1 play #2, but something about that just doesn't sit well with me. It's like there's some reward for coming in 2nd. If you're going there, you may as well do the four-team format...
Personally, as a purist, I wouldn't go with the scenario where #1 gets a bye while #'s 2 and 3 have a playoff to see who plays #1, because to me that's the
opposite of purist...
I do exclusively historical and for the majors I stick with what was done historically, except for a few tweaks here and there (like not having best-of-nine from 1919 thru 1921, not always using the same home-away formats or same amount of travel/off days...). For minors, though, when I have them and they are single-league/no-division, I have the top two teams play for the title if I don't care about what really happens (lower minors, for example), but for minors where I
do care (IL, PCL, AA, maybe Tx Lg, Southern Lg, Eastern Lg) I might do formats #2 or 3 above...