This is interesting. I just went and looked at the league leaders for CF plus plays in Cooperstown, which is near the end of the regular season (155 games played)..
The CFers with the most plus plays both have 17. One guy has a more "traditional" CF arm (defensive ratings of 91/85/61/75), the other has a SS arm (89/85/85/82).
Looking through the game logs and box scores where they had their plus plays, the first guy had 13 on fly-outs (denoted by yellow ++ in the PBP) and 4 on base hits (denoted by green + in the PBP). The second guy was almost identical at 12 and 5.
So looking at these two guys, the difference in arm ratings seemed to have little to no impact on their plus plays, as they had the same number of play distributed nearly identically.
But when I did the analysis of my player, Amos Taylor, almost a year ago, it seems like the majority of his plus plays were on base hits. Unfortunately, I did not note any specific numbers in my ticket, so I don't know exactly what the breakdown was at that time. Maybe he just had an unusual variance by chance at the time.
I guess the only thing I can surmise now is that the plus plays noted by the yellow ++ are due to range, and the one noted by green + are due to arm.