May as well explore this topic just for fun since this should be a simple "yeah or nay" but it's not.
I've never seen a stock moped equiped with anything except metal screens for filters. These screens are sized to allow small stuff to pass while trapping stuff too large to get through the main jet.
Gravity feed is easily slowed by any additional resistance to flow. I would avoid a paper, sintered bronze or any other fine filter or a filter with an area that is just too small. Add any filter or screen and flow slows somewhat.
Measure the inlet and outlet holes of the filter and chances are they are smaller than the inner diameter of the fuel line, so some flow resistance is pretty much guaranteed no matter what.. (The "1/4 inch" inline filter in front of me has a 0.15 hole and the fuel line has a 0.20 inner diameter.) The shoulders created by the end of the filter's nipple is another slight restriction.
If fuel was pumped under pressure it would be a different story. But even in a automobile gas tank, upstream from the fuel pump, they only use high flow metal screens.
Another thing i don't like is creating additional spots for fuel leaks. Cut a line and you get three.. One on each end of the filter and the filter body itself.
The plastic will melt if it touches a hot engine so placement is something to think about.
Then you gotta throw them away when they are dirty.. (big deal.. a buck or two) But how do you know they are dirty? After a few months they are no longer transparent. You can't open and examine them because you gotta break them to do it.
The screens in the tank and / or on the carb are easily examined, cleaned and reinstalled. Adding filters adds potential problems while solving or preventing none.
Kreem the tank, use clean fresh fuel, replace delapidated fuel lines and get a good gas cap and the stock filters are more than adequate.