animal, was your friend possibly T.Webb? cause i know you guys teamed once and we are pretty tight
anyways, when edgeguarding Fox, you base your edgugarding off of where he is coming from just like with every character. if he is going to illusion to get ack onto the stage, downsmashing and downtilting work great. Also YL's nair is another good option since it out prioritizes it. as for the fire fox, again, your nair completely owns it, and if they are at a lower percent you can generally land another nair if the first one hits near the end of the sex kick.
as for trying to hit them while they are off the stage, it helps to try and automatically try and cover a few options that you know fox can take. for example, simply shooting an arrow off the ledge will make it so they cant sweet spot with the illusion because they will just hit the arrow. this works similarly with a boomerang. bombs also work if they hit them close enough so that you could follow up with a nair or something but they also can cause them to mess up a sweet spot.
I also like to dash attack sometimes cause its really quick and hits higher than the downsmash can