Agree with waiting since you have more offensive starters required than IDPs, but it does depend a lot on scoring. If you get, say, more than 3 points for sacks/INTs and/or count TDs from your IDPs, you would do very well to grab Watt In an early round (maybe fourth or so, depending on what offensive players are available). If there are no elite QB/RB/WR on the board then, I'd definitely grab Watt. There are plenty of LBs and DBs to go around, since you only start 2 each. Quality DLs, as MAC said above, do tend to be more scarce, so I'd look to those first when you do start selecting DLs, but I'd probably fill out my starting offensive positions, and maybe even a couple of backups, before jumping over to IDPs.
As for bench, I'd probably get one quality backup (keeping an eye on bye weeks) for DL, LB and DB. Fill the rest of your bench with solid offensive backups.