According to the fangraphs guys they are hearing the cubs are looking at Jackson Kowar(RHP Florida), and Steele Walker(LH probably CF Oklahoma). I've also read that they intend to go after some guys with upside. So, wouldn't surprise me to see whoever they go after with the first pick to potentially be a below slot deal. The draft is really heavy on prep arms from like 20-50 and it's pretty deep because of that. But the college crop is kinda meh it seems.
Walker can hit(.327/.406/.517 over 3 years) but doesn't excite me that much because he's probably a LF only guy. Kowar is a bit more interesting. MLB.com has him with a 65 fastball, a 60 change and a 50 curve. He's got good size(6'5 180). Only issue is he might not be there at 24. If neither of those two guys are the pick I'm not entirely sure who it'll be. Only 13 of the top 30 prospects are hitters. And of the 17 remaining pitchers, 10 are prep guys and the other 7 college guys are mostly slated in the top 15. Mize is probably the #1 pick. They had Singer #5, McClanahan #9, Gilbert #17 and Rolison #26.
If none of those college arms is available, there's probably not a ton of college bats. And I doubt they'd go with a HS arm unless it was real value. So, if that happens, I guess what they'd likely do is either draft a HS bat they like or look for a underslot deal for a college bat they like so they can use the money they save to potentially overpay someone who slips to their 2nd round pick because of signability issues.