There is a lot of moving parts in this space, which is ever evolving.
Co-sponsors deals seem to have generally all but left. In this relationship, a (typically) unlicensed party raised money for the "main GP", and was given a share of the GP. In exchange they brought the capital and managed the Investor Relations for the investors this person brought to deal. In this scenario, typically, the actual LP (you, Cheryl) are invested in the actual offering led by the "main GP". There is one set of legal documents that you signed into the main offering, you funded the main bank account, you get a K-1 from the same entity as every other investor. A reason the "main GP" may be saying they don't want to deal with you is because per the SEC rules, GPs must have active involvement in the day to day of the actual offering, so if "main GP" starts doing the communication with you, it can be viewed as the co-sponsor no longer having active involvement, and create SEC scrutiny for all parties of the deal.
That SEC scrutiny did happen many years ago across the industry. It resulted in many "co-sponsors" getting their broker dealer license and raising capital for outside investments in a more black and white way. But there are a lot of "main GPs" that either don't know there was scrutiny or figure since there seemed to be no major action, the SEC blessed the relationship (but didn't change the rules, so who knows when it will rear its head again).
Enter the "Fund of Fund" model, which is more commonly truly a feeder Fund. A true fund of funds would mean the FoF raises capital into a single offering, and then that offering is invested across multiple other investments. A feeder fund is a single offering that is all funneled into another single offering. These were launched because all those "co-sponsors" that didn't want to get licensed needed a cleaner way to be in deals. High level, relationships remain the same. The Feeder Fund sponsor goes out and matches their network to a "main GP's" deal. The difference: the feeder fund is the LP in the "Main GPs" deal, and you are an LP in the feeder Fund. As such, you would sign docs for the feeder fund, you would send your investment to a bank account controlled by feeder fund, and the K-1 you are getting is from the feeder fund. Effectively, it just adds another layer. The Feeder Fund GP (FF GP) is the person that used to be the cosponsor. That person has negotiated a cut of fees and carry with the main GP that actually operates the deal. The FF GP does not need to have a FINRA license, because they are now a GP of their own offering. In this arrangement, similar to the co-sponsor arrangement, if you reach out to the "main GP", you are NOT an investor with them. You are an investor in the Feeder Fund, and the Feeder Fund is the LP in the main GPs deal.
At the end of the day, the legal arrangement has changed, but the functional arrangement is basically the same.
The pro of a feeder fund is if you trust your FF GP and they are well connected, they can be performing due diligence on multiple operators. The downside is it is another layer of costs (legal, accounting, possibly more splits and fees), a second layer of communication, and effectively needing to vet two groups, the main GP and the FF GP.