"AngelList Platform LPs" are LPs who discover a syndicate or a fund via the AngelList Platform and are attributed to AngelList. "General Partner LPs" are any LPs that are not AngelList Platform LPs.
Under the traditional carry model, AngelList receives 5% of the carry for investment advisory services rendered to the fund, but waives the 5% carry for all "General Partner LPs". As a result, a General Partner always receives the full 20% carry (or whatever carry amount they set) on the investment made by all "General Partner LPs".
LPs do not pay any other fees directly to AngelList, but may pay management fees to a Fund Lead and will bear a pro rata share of any administrative fees paid by the applicable Fund or SPV.