I don’t use such cars, I drive mainly standard Kunos cars, and at most 2 dozen proven mods. if interested, a decrease in performance occurred when using a Ferrari 512 TR, again on Fonteny on the same car there is no such thing, that's why I askedPeople often forget the cars themselves can cause issues... If they are "4K", unoptimized, etc, it could slow things down considerably.
That and the FOV of the TV camera changes the LODing of the trackside objectsYou can also turn a bunch of stuff off in cockpit view in CSP so it's not all that weird to have external cams run at way lower FPS than when you're driving.