Each species has their own pos and cons. You can build your own species using HomeBrew.

Origins mod creator - Apace

Species

Human

Nothing special.

Felinid

Cat-Like: They posses silly cat ears and scare creepers away.

Strong Paws: As they run, they gain speed over time.

Nine Lives: Have 18 maxium health.

Dwarf

Small Stature: They are 1,2 blocks in size.

Short Arms: Deal 20 percent less damage then humans.

Small Lungs: Breathe twice as fast as humans.

Moth

Exoskeleton: They walk 50 persent faster than humans, but swim 25 percent slower.

Ledioptera: Have elytra on their backs.

Flammable Fluff: Take 5 times more damage from fire.

Jelly Person

Jelly Body: Very bouncy,

Gas Bags: Breathe five times less frequently than humans.

Viscous Flow and Crystallization: Take 50 percent less damage from falling and 20 percent less from melee attacks, but 40 percent more from projectiles and 50 percent more from cold.

Dissolution: Get weakness effect when in water.

Lizard Person

Heavy Scales: Walk 10 percent slower than humans.

Tail: Deal 1 extra damage on any melee attack, but cannot wear leggings.

Cold-Blooded: Take 30 percent less damage from projectiles and fire, but 30 percent more from melee attacks and 70 percent more cold damage.

Ningyo

Gills and Fins: They swim 75 percent faster than humans, but can breathe only underwater.

Claws: Deal 1 more damage.

Weak Bones: Have 1 heart less maximum health than humans.

Yowie

Gigantism: They are 3 blocks in size and have 22 maximum health. 2 players can seat on them.

Heavy Body: Swim and walk 15 percent slower than humans.

Powerful Muscles: Deal 3 extra damage.

Powerful Lungs: Breathe twice as fast as humans.

Salamander

Larger Stature: They are 2 blocks in size.

Native Element: Immune to fire, ignite the ground beneath their feet, and swim in lava 150 percent faster than humans. Any damage they deal sets the target on fire.

Temperature Shock: Take 6 freeze damage in water.

Fragile Shell: Have 1 heart less maximum health than humans.

Svartalfar

Vulnerability to Sun: Burn in the sun.

Underground Glory: Gain haste when the Y coordinate is below 40, but gain weakness when it is above 40.

Adaptation to Underground: Have night vision and a body size of 1.6 blocks.

Ent

Thousand Trees: They are 2.5 blocks in size, have 26 maximum health, and walk and swim 25 percent slower. Have knockback resistance.

Photosynthesist: Get saturation 2 during the day but hunger 2 at night.\n§lLenticel:§r\nBreathe five times less frequently than humans.

Lenticel: Breathe five times less frequently than humans.

Cellulose Body: Take 2 times more damage from fire.

Tough Bark: Take 10 percent less damage from projectiles.

Yanme'e

Two Pairs of Wings: Can fly if they run and look up.

Insectiform: hey are 1 block in size and have 10 maximum health.

Unggoy

Methane Breathing: Can't breathe and must drink underwater breathing potions to survive.

Hard Shell: Have 2 hearts more maximum health.

Adaptive Exoskeleton: Change their shape under certain conditions.

HomeBrew

Changing Species

You can download the subpack with the recipe for the species change potion.

Uses player.json and beta APIs.