I'm not a fox main, but in general I follow 3 main rules when fighting Bowser with any character
1. Don't challenge anything, wait for Bowser to whiff than punish.
2.Try not to instantly shield after every scenario, because Bowser players love to go for down b shield breaks
3. Avoid rapid jabs because Bowser's tough guy armor ability makes it so he doesn't get stunned and he can hit you out of it.
Point 2 and 3 are irrelevant. Rapid Jab doesn't really have protection from tough guy, his tilts do. His rapid jabs are actually nearly pointless for regular use. In fact, any high to top level Bowser will echo this without hesitation. Point 2 is irrelevant unless you play against casual Bowsers. The higher level option is generally side special, his command grab.
The only point to take away from this is point 1. Don't shield Bowser in general. Force impatience in the player and have them whiff an attack, then go nuts because you're Fox and can peel his face off in less than 5 seconds.
My own input is the same as the point 1 I replied to as well as Fire Breath. Since it's a telegraphed move, learn to spot what the startup animation looks like. If you have space, do a dash back and spam laser until they stop breathing, then punish the end lag with a run in fast fall Nair uptilt string. If you are in the corner when they approach with Fire Breath, just jump over them or hit the platform above them, and punish accordingly. Since command grab (side special) is also very telegraphed, mentally train yourself and your muscle memory to spot dodge it, and then punish it accordingly. These are the general rules of thumb to fighting Bowser in neutral. If you want to go into depth when it comes to edge guarding Bowser, it's a lot more complicated than this and would require an extensive amount of writing or a video to cover it. Depending on the situation, I might be up for it based on what replies appear, but I'll hold off on it and see.