Rosy
Smash Apprentice
against fox, you should be spacing fairs and nairs and switching them up. You should also do fade away fairs and nairs>jabIn what situation is Fair better than Nair? I can't seem to find a reason to use it.
by doing the jab you could potentially catch them off gaurd and put them in their sheild which is then a good point to add sheild pressure or try to poke them with a d smash.
fairs are particularily good when you expect a slow get up. If you learn to space your fair you can punish these get ups and will be able to cover more ground.
Besides that I dont think its a viable kill move to I would limit fair to those two options.