Can he do all of that? Yes.
Can he get much better at doing all that? Also yes.
This video shows what he can do. Now he just has to make it his everyday play style.
As for making the current receivers look good, those very receivers may make Fields' life easier. Mooney in 2020 and Pringle in 2021 were two of the top (if not the top) receivers in separation. Separation by receivers is going to make Fields' reads much simpler and quicker.
As for St. Brown, his combination of speed and height is going to open up the middle for everyone else. Hopefully, he can gel with Fields and become much more effective than he was in Green Bay.
I would not be against adding a shorter player like 5' 10" Skyy Moore or 5' 9" Calvin Austin III because they both seem to be separation machines, not to mention track stars. People seem to have forgotten (or were too young to have heard of) the Marks Brothers, who were two unrelated (Mark Duper and Mark Clayton) 5' 9" Dolphins WRs, who took the league by storm when Miami drafted Dan Marino.
A really tall receiver was more Trubisky's type of receiver because he was inaccurate and needed the large catch radius. Since Fields is more used to seeing open receivers before throwing to them and is accurate, wouldn't it be better to have 3 receivers (Mooney, Pringle and Skyy/Austin) who are top of the list in separation?
Of course, I would not be against a Christian Watson who has height, weight and speed if he is good at separation. But he will be more expensive, draft capital-wise than an Austin.