Most Part 125 airplanes are pax limited to around 40, as I recall. I addition you cannot hold out for charter unless the pax are of a similar nature. Sports team are a good example. The biggest sector of Part 125 in the US is probably 737BBJ operators although there are some on Part 135 which is more restrictive yet regarding payload. Donald Trumps 757 is a good example of a Part 135 operator.
Part 125operators use Opspecs as apposed to LOAs, aka Letter of Authority.
Part 125 is a pretty lose operation compared to either 135 or 121. The FAA has been saying that they are going tighten up this section of the FARS, but unless it has happened recently I don't think much has changed,