Do Top Level Pros (meaning Elite / BPT anglers) have agents / managers which handle sponsor contracts, appearances and general business activities for their individual brands like other pro athletes?

Not sure, But I imagine its a family affair. Maybe a few of the top tier guys have someone handling it.

A few do but for the most part they do it all themselves or as BMCD mentioned, they have a spouse or other relative that does a lot of that type of work for them. Many however hire people to edit videos and/or do their social media for them. There have been several agencies or individuals that have done some rep work/sponsor acquisition for Tour level pros but I don't think or know of many that do it anymore.

I represent KVD and few other pros everytime i fish one of the baits they sponser.

As Clark state, a few of them do.

Professional Edge Fishing

A lot of their wives do a bunch on the business side.