I'm assuming you can't have a flex player that is RB/WR/TE.
In a non-PPR, it doesn't really matter IMO as to whether or not someone could get an advantage by having 3 stud RBs (I'm not sure that I agree with that anyway, but let's go with it). If everyone goes into the draft knowing the rules and they draft with a plan, then everyone is on equal ground. Everyone plays by the same waiver wire rules.
Injuries are going to be a huge factor, especially in the RB position. Almost no one will have the same flex player at the beginning at the season that they will have at the end of the season.
Personally, I would go RB/WR since trying to put 2 usable TEs on a team is more difficult and that might deplete the TE availability on the waiver wire for those that need one due to injuries or bye weeks. Especially if this is a 12-team league.
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