In a nutshell, it does to Immersive Armors
what MLU does to Vanilla armors

Specifically, they've been rebalanced so as to compliment MorrowLoot Ultimate. Without patch, things get a little incoherent. Immersive Armors' stats will now more closely resemble comparable vanilla armors in a way that they are usually a "pretty" alternative. Some have been hand-placed.

Many recipes have been penalized (racial skill penalties, Skyforge-only for Ebony, quest and faction requirements now mandatory). Why, you ask? Just to make it more "hardcore"? No, because these armors have been made more powerful than easier recipes. Take a moment to craft your best available equipment - slower leveling makes it more rewarding.

In fact, this solves the balance complaints some have had with Immersive Armors: you no longer have overpriced equipment dropping everywhere, craftable recipes that outclass everything else with the same requirements, or modern Civil War gear being found in ancient tombs.

Instructions for use:
Install Immersive Armors and the patch at the same time. If Immersive Armors is already installed on your save file, the patch may not customize your MCM configuration correctly. If you already have IA installed, uninstall it, save, clean your save file, and install both at the same time.
Do not re-enable world-distribution options of disabled armors in the MCM. You may still disable whatever you like, as well as switch around light/heavy variants and colors.

Below I will list the armors which have received significant changes. Many more have received small balance changes that aren't worth highlighting. Descriptions are in the context of an MLU installation (Daedric > vanilla Daedric).

Alduin Scale: on par with and heavier than Daedric, you must complete the main questline to be able to craft. Requires Dragon, Daedric, and Arcane perks - but not the hidden requirements of Daedric. Not found anywhere.

Apotheus: A tier above Scaled, requires Advanced perk and Sleeping Tree Sap quest completed. One set can be found.

Bosmer: Light equal to Elven, Heavy slightly better than Dwarven, requires the Elven or Dwarven perk and Smithing skill 40 for non-Bosmer to craft. Not found.

Bosmer Engraved: A tier above Scaled, requires Advanced and Smithing skill 60 for non-Bosmer to craft. Not found.

Bosmer Wild Hunt: On par with Dragonscale/plate, requires Dragon perk to smith. Does not require Ebony to craft so can be forged anywhere. Not found.

Brigand Dwemer Breastplate: The only Dwarven piece craftable without Ancient Knowledge perk, it's slightly weaker than Dwarven Armor but heavier. Recipe requires Dwemer Plate Metals instead of Dwarven Ingots and the Dwarven perk. Found randomly.

Daedric Lord: On par with Daedric and has the same crafting requirements. Not found.

Dragonbone Ebonsteel: On par with Dragonplate/scale, requires Dragon and Ebony perks. Ebony required to craft, so Skyforge-only. Not found.

Dragonhide Robe: Slightly less protective than Dragonplate/Scale, requires Dragon perk to craft. Not found.

Dragon Knight: On par with Dragonscale/plate, requires Dragon perk to craft. Ebony in recipe, so Skyforge-only. Not found.

Dwarven Mage: Slightly less protective than Dwarven/Elven, requires Dwarven perk and Ancient Knowledge to craft. You may toggle Light/Heavy/Unarmored, but Light variants will be found in Dwarven ruins uncommonly (nowhere else). Benefits from Ancient Knowledge buff, which means Light Armor smiths can now benefit from Ancient Knowledge!

Ebony Mage: Slightly weaker than Glass/Ebony, requires Ebony perk and Skyforge-only. Not found.

Glacial Crystal: A tier above Orcish/Bosmer Engraved, requires Ebony/Glass perk to craft. Glacial Crystal Ingots can be purchased from blacksmiths. Will be found on higher-level enemies, so disable distribution if you don't want to see it semi-commonly at high levels. It's on par with (Ancient) Nord Hero equipment.

Hedge Knight: Slightly adjusted, you may want to enable distribution. It's disabled by default in IA but I made sure it'll be balanced when you encounter it.

Heroic Imperial: On par with Orcish, requires Advanced perk and Imperial faction and Civil War quest progression to craft. Found only on Imperial officers.

Heroic Stormcloak: On par with Orcish, requires Advanced perk and Stormcloak faction and Civil War quest progression to craft. Found only on Stormcloak officers.

Imperial Knight: On par with Ebony, requires Ebony perk and Imperial faction and Civil War quest progression to craft. Ebony in recipe, so Skyforge-only. One set worn by Legate Rikke.

Ritual Boethiah: On par with Dragonscale, but much cooler, requires Boethiah quest completion and Dragon perk to craft. Not found.

Stormlord: On par with Ebony, requires Ebony perk and Stormcloak faction and Civil War quest progression to craft. Ebony in recipe, so Skyforge-only. One set worn by the big man himself.

Tribunal Masks: Requires Arcane perk to craft. Not found, but sometimes sold by Neloth.

Tribunal Robes: Requires Arcane and Glass/Ebony perk to craft. Heavy variant has Ebony in recipe, so Skyforge-only. Not found randomly, but sometimes Red unarmored pieces are sold by Neloth.

Vvardenfell Glass: Same as Glass, but requires Smith skill 80 for non-Dunmer to craft (vanilla Glass favors Altmer). Some hand-placed pieces found on Solstheim.