Top Speed - Very rarely are fighters like the F-16/F-18 operating close to their max speed. Max speed of the F-16XL would most likely be lower than the F-16.

Maneuverability at high speeds (Supersonic) is not very important since the speed will all fighters have their sustained corner velocity well below that and therefore will drop to that speed quickly during their first turn in a dogfight. Since the F/A-18 is a dual engine plane it will outperform the F-16 at higher altitudes. It is only at lower altitudes the F-16 is superior.
The F-16XL would be a poor dogfigthter compared to the F-16A/C due to its wing profile.

Payload - You can't determine anything from the amount of stations. Planes can carry more than one munition on a single station and even though a normal F-16 has 9 stations doesn't mean it can carry for example 9 MK84 2000 lb bombs.

Your Final note all depends on the avionics suite you put in it. Another thing to take into consideration is the F-15Es higher survivabilty due to its two engines.