The e-clip setting only fine tunes the jet needle setting to work well with the main jet and the temp. The main jet needs to be adapted to temp and altitude. If you have the correct main, then you can move the e-clips to get rid of stutter and hesitation through the range of carburetion.
There is no fan belt on Polaris fans. The only belt is the drive belt, the tension on which can be altered using spacer washers inside the secondary clutch if needed. As long as the primary isn't shaft isn't riding significantly at idle, it probably isn't a concern.