So that's just it? If you make your Mii small and fat, it'll be both fast and strong with no drawbacks whatsoever, but big and thin and it'll be terrible in every way?
There better be something else to it, because that sounds awful.
It feels that way. I went into the lab and test out how they were launched. I used Mario as my constant variable and attack with Uncharged Fsmash, Dsmash, Usmash on each candidate. I wanted to see at what percentage did they KO. (Disclaimer: Data not set to stone and human error may occurred during the experiment. Please bare with me.)
Testy (Small, Lightweight, Swordfighter)
Fsmash - 107%
Usmash - 124%
Dsmash - 160%
Test 2 (Tall, Lightweight, Swordfighter)
Fsmash - 107%
Usmash - 124%
Dsmash - 158%*
Fearitself - Personal Mii (Tall, Medium weight, Swordfighter)
Fsmash - 108%
Usmash - 126%
Dsmash - 161%
Fatesty (Small, Heavyweight, Swordfighter)
Fsmash - 109%
Usmash - 128%
Dsmash - 162%
TooFat (Tall, Heavyweight, Swordfighter)
Fsmash - 110%
Usmash - 130%
Dsmash - 161%
I doubt the class has any effect on the KO percentage but I put there just in case. Now about the * . Dsmash is sort of weird. Normally, I know I KO a Mii when the Red Eyes-Black Lightning Appears but Dsmash cause enough force that the Miis just die without the KO effect. Anyways, that is my results.
If you still feel that my experiment isn't incorrect, free to perform the test yourself. I used Mario on Battlefield Omega Mode. The Mii were in the middle of the stage when attack. I sweetspot with Fsmash and hit the first part of Dsmash. Perform the Trial at least 5 times before recording the result for precision purpose. I hope that helps. Thank you.