First off, since this is standard you’re gonna want to lock in your workhorse backs, if you dont have 2 solid RBs in a standard league you’re at a huge disadvantage.
As for your 2 RBs I’d go Howard and Freeman. They both have secure floors and high ceilings. We have 2 years of evidence of Howard being a stud, and we have 3 years of evidence for Freeman. McKinnon is in a situation that could be phenomenal for fantasy, but we just dont know what exactly his workload will be in comparison to the other 2 backs, and we dont know how we will perform. All we can do is project with him, with the others we actually have evidence.
And hey I could definitely be wrong and McKinnon could blow up, but barring injury Howard and Freeman will both definitely be top 20 RBs this year, and I like to go risk-avert with my early picks/ keepers.