What IVs and EVs do NPC trainers' Pokemon have?

Question

I've read here that NPC trainers' Pokemon do have natures (from Gen III onward) and IV's, and I've seen it mentioned in a few places that at least the Elite Four's Pokemon have EV's as well, but I've found no exact or even, seemingly, certain information on the subject. Basically, are NPC trainers' Pokemon's natures, IV's, and EV's randomly generated, or, if they aren't, what are they? I'm most interested in information pertaining to Emerald, but any such information pertaining to any of the other games would also be very much appreciated.
Also, please cite your sources (or l33t hax0r credentials as the case may be).

Comments

I remember reading in an answer to a different question that Gym Leaders are 20 or 25 across the board I think.  E4 is higher.  Don't know how much.  I would also assume that certain prominent NPCs also get Pokemon with specific Natures, IVs, and maybe even EVs, but I don't know about that.

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The IVs and natures are set, but they're probably set at random.

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For Platinum:
https://www.dropbox.com/scl/fo/ai4wal71xvjdhoc040a1l/ALMKWnwoHLyI4DZTDKehdnU?e=1&preview=Pok%C3%A9mon+Platinum+-+Script+File+(Piplup).xlsx&rlkey=ly98psc5r7ju9f3y1d1g30jov gives IVs, EVs, and movesets. The Chimchar file does the same thing, but there doesn't seem to be one for Turtwig. The sheet also doesn't give Trainer names, but it's pretty easy to figure out who's who.

Answer 1

Here's an answer pertaining to Emerald.

All trainer Pokemon have a difficulty value between 0 and 250. The game takes that value, divides by 10, and gives them EVs and IVs equal to the result. Most trainers get 0 to 100, but the elite 4's Pokemon all get a difficulty value of 250, so they get 25 evs and 25 ivs.

By cross referencing between this list of all trainer data and an IV calculator, you can confirm this.

I believe natures are assigned at random? They seem to be fairly random

Comments

In gen3 games, the difficulty value goes up to 255, and to get the iv you multiply by 31 and then divide by 255 and round down
Difficulty value 250 = 30iv, 255 = 31iv

Answer 2

The IVs and Natures are randomly determined, and the only EV trained Pokemon are the Elite 4 and the Pokémon in the PWT in Black/White 2.

Cynthia's Garchomp, however, has perfect 31/31/31/31/31/31 IVs in Platinum. So... Yeah.

Source: Experience and Bulbapedia

Comments

How could you know this about hidden in-game mechanics through mere experience? It'd help to reference the Bulbapedia article that contains this information, because as it stands this answer doesn't sound very credible.

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I used a cheat to capture other trainers Pokémon and then used Showdown! and Serebii to determine the IVs and Nature. Hidden Power dude helped me a lot!

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Cynthia's bullsh*t 6iv Garchomp wtf I want a 6iv garchomp

Does it have EVs too?

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252 EVs in accuracy, crit chance, and flinch, but only when using Dragon Rush at the worst possible moment for you.

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Also 510 EVs in hax.

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According to Speedrun.com, many other trainers' Pokemon in BW, including some Team Plasma members, have EVs. Cynthia's Pokemon have 30 IVs in every stat.

Answer 3

In 7th generation at least, (I imagine this is retained in Sword and Shield) some Trainer classes do EV train their Pokemon. I know this because I was battling a Veteran with a level 36 Gabite. My Leafeon had 86 speed. Even with a Speed boosting nature and perfect IVs Gabite would top at only 82 speed and yet it outsped me. It makes sense veterans would EV train their Pokemon but I don't know to the extent how much this applies to other trainer classes.

Answer 4

This spreadsheet and this other spreadsheet should have exact levels, natures, and stats for every trainer in Emerald. They unfortunately do not have exact IVs and EVs, so I guess you can try putting them in this damage calculator to estimate their IVs and EVs.
source