You have a proper draft, which means assuming you play with the OOTP dev engine and turn scouting back on (and on low, but that's a personal prefrence), you can play in much the same way you would a modern game, with proper management and guesswork and all. The first decade or two will still be fairly on rails as many of the big players are already past their "learning" stages (1919 being the earliest historical minors can be a thing, so Ruth for example is already on the way to becoming the legend he became) but it seems like it'll start diverging after that to a degree. I would recommend against lowering the TCR though as some suggest for historical play due to this now mind you.
Draft size of course depends on what year, as the minors star off really small, and are more of an indy league than true minor at first.
By the way if you're playing around 1960/1970, make sure to draft a little known guy named Randy Poffo, more famously known as OOOOHHH YEEAAAH MACHO MADDNESS. *snaps into a slim jim*
But here, went and did an example sim for you with default settings, and here's the 1920-1921 draft pool announcement.
Yep, that's a 17 year old Lou Gehrig, up for grabs for any team. Will be interesting to see how he develops without ALS.
For the record in this example playthrough he ended up signed by St Louis after Philly drafted him but failed to sign him before the deadline.
The drafts go really long at start though due to high number of player and low number of teams, the 1920 draft was 70 rounds.
Also here's the 1st round picks for anyone whose interested.
