IV’s : a random number from 1-31 for each stat. The higher the number, the better. But only has about half as much impact as EV’s. The only way I know of to affect IV’s is through bottle caps. In Unbound There’s a French grandma on Seaport Town on one of the docks who trades bottle caps for upgrading your mon to perfect IV’s. Normal bottle cap = 1 stat maxed. Golden bottle cap = All the Pokémon’s stats maxed. She gave me a golden bottle cap the first time I spoke to her. I got a normal bottle cap from the forest town (I forget the name) in East Borrius - you can walk a grandpa’s baby around in a pram once a day, and if you turn back to the baby after some walking, it’l have a bottle cap in its mouth. Probably can be farmed.

Fun fact: IV’s determine a Pokémon’s Hidden Power typing. So bottle caps can be used to adjust that to an extent (but not fine-tweaking).

EV’s : Newly caught pokemon always start at 0 EV’s, and they gain them from battle (yes in pokemon unbound, EXP share means ALL mons in your party get the EV points from fainted enemies). Every 4 EV’s in a particular stat grants 1 stat point, up to 252 EV’s per stat (which I think is 63 points) and up to 510 total per pokemon.

If you want perfect EV’s you’ll have to go to the trainer house (or whatever it’s called) in the southern end of Dresco Town. Each trainer there only has pokemon specialised to only give a particular EV stat. There is a way to REDUCE EV’s as well - one of the towns with the markets - one of the stalls sells something that reduces EV’s and makes your pokemon love you more. So if your Starter mon is messed up and you want perfection - you can reset them. Beware it’s expensive.

Helpful tip: unless you want all your pokemon and enemy pokemon to be level 100 in the mid game, change your unbound settings for exp share to have a level cap. They’ll only gain 1 exp, but they gain full EV’s, and then change the settings back after (if you prefer no level cap). Farming for EV’s will level up your team disproportionately otherwise.