well i like to hold a turnip in my hand and use alot of ground float cancelled arials and an Fsmash every now and again, and when ever they tornado, just shield it and if they retreat with the nado u can chase em with a glide toss and get em before he can do anything about it, and if he stays on u, well u can just ground float a Bair or Nair to punish.
when he's planking and has the lead u want to do a mixture of throwing turnips and playin alot of mindgames NEAR the edge, just at that range where he thinks he just might be able to shuttle loop u and punish but far enough away that u can run in and out of safe/danger zone as to bait him into using it. and when he does u can clank with his glide attack with a Bair and maybe even nair works too, but point is, the clanking is good since u can cancel your arial and he has to suffer the landing lag, if he attacks low out of the glide attack, then u can punish with a Nair OoS.
if you are having trouble getting back on stage just remember to not challenge MK offstage unless you absolutely HAVE to just to make it back, if you recover high u can beat his shuttle loop if u space your Dairs correctly, when u are at the max height of his loop u can Dair, if he closes the gap, you most of the time don't have any choice but to take some damage, but eating a Dair or Uair is better than being killed with a shuttle loop. if you recover low, make sure u make good use of your float/double jump and on rare occasions toad, and remember he has an extremely difficult time punishing our parasol so use that whenever he's above u coming down.
but i guess on this MU its good to stay grounded a good amount of the time but its important to know when to go into arial mode, you just have to learn to catch on to some habits and punish them.