Hog's Morphs
Hog's morph is an old addon. It sadly uses player.json as again, it's an old addon. But as long as your not playing with other addons.
Experimental Toggles -

Explanation Video -
Tags -
Giving a player a tag with the addon will change attributes.
Activate it by doing /tag @s add (tag name)
Or remove it by doing /tag @s remove (tag name)
Tag list:
NF - remove fall damage
NW - no wither damage
LD - no lightning damage
NE - no explosion damage
WD - Water damage (like enderman)
FI - Fire immunity (no fire damage)
KBR - no knockback
GC - grows crops (like bees)
BD - burns during the day without helmet
FL - allows flight
player - all mobs attack
villager - attacked by zombies
fish - attacked by guardians
arthropod - attacked by iron golems
animal - not attacked
undead - attacked by iron golems
1-40H - changes amount of health (only works if its even)
100H - gives 100 health
1-10D - changes amount of damage dealt
1-10WS - changes the speed in water
0-10S - changes speed on land
V0-80 - changes the model of the character.