QBs who run more generally have a lower floor.
Using ESPN PPR scoring (4 point TD pass), Fields' weekly scores are:
11.94
11.38
18.4
31.98
15.94

Cousins' range is a little dicier
6.2
17.54
11.1
7.52
34.36

He doesn't run enough.

The other two guys don't run much either except...
well, William actually has run quite a bit this season.
His weekly scores are
7.22
7.36
17.32
11.48
23.56



By the numbers, Fields is the obvious choice.
As long as he starts, he's the guy I'd want over the other three.