The MCM options I use are as follows: I disable running drains stamina and animal poisons paralyze (the double vision is bad enough). I enable better archery and widen the NPC archery spread a little. I make sure you can't bull rush a friendly NPC to avoid accidental assault charges from sprinting past someone in town. I set it so choosing either health or stamina on level up increases carry weight by a couple points. That's all I can remember at the moment. I think everything else, I just leave at default settings.
As for mods, I too use Immersive Patrols (with Requiem patch).
I use some graphical/sound/weather mods (Official High Res packs (optimized) SMIM, Skyrim HD, CoT 5.0, WATER, SFO, Amidianborn, Audio Overhaul Skyrim, and Dyndolod) and UI mods (SkyUI, Racemenu, iHud, Less intrusive HUD and Warburg's Paper Map).
Also I use several of what I consider bug fixing type mods like Violens, flora respawn fix (with Requiem patch), Kryptopyrs Clotheing and Clutter Fixes, Weapons and Armor Remade and Complete Crafting Overhaul (with Requiem patches by Unmeix), NARC, Convenient Horses, http://www.nexusmods.com/skyrim/mods/72321/?and Better Quest Objectives.
Then a few mods with Requiem patches to spruce up magic a bit more: Apocalypse, Wintermyst and Immersive College of Winterhold.
Then Frostfall and Wet and Cold to add some cold atmosphere. And http://www.nexusmods.com/skyrim/mods/71708/? to make eating and sleeping a bit more immersive without adding in mandatory eat/sleep requirements.
Notice Board to add more radiant quests.
ETaC and JK Skyrim (major cities only) to spruce up towns and cities.
And of course Alternate Start. I really didn't like the vanilla start much at all.
Then I have made a bunch of personal mods to tweak a variety of things to suit my own personal tastes, including revamping some of the archery and smithing perks, rebalancing certain weapon and armor types (more on that below), added or modified some of the blessings conditions (like adding a condition where Arkay won't give you a blessing if you take any necromancy perks, since Arkay hates necromancers), removed some of the visual spell effects from Healing Aura spells, and a whole bunch of minor tweaks to numerous to list and most of which I cannot even remember of hand.
Basically, whenever I encounter something in game that I think should be handled differently, I whip out x Edit and change it. Most recently, I decided that you should not need quicksilver ore to cast an animate lockpick spell, or at least the ore should not be used up when you cast the spell. That was something Ogerboss put in for balance to prevent alteration from being all out "better" than lockpicking. I'd rather have roleplaying options than balance and I though it was annoying for my mage to have to lug around a sack full of ore just to open a few locks, so I got into xEdit and removed the script from the spell. I have made literally hundreds of little tweaks like that.
One of the most significant changes I made was to rebalance scale, Dwemer and Orcish armor and weapons. I wanted to be able to have a character that identified with a particular armor type and be able to use it through most of the game. I also wanted to bring back the concept of medium armor from Morrowind. So, I increased the weight of scale slightly and dramatically increased the protection it offers, making it on par with glass in terms of protection, but weigh about twice as much (which is a big deal in Requiem because of the "mass effect" system). Since scale weighs twice as much as glass, it is quite inferior despite being able to offer a similar amount of protection. Since light armor never provides all that much protection in Requiem anyway, having scale provide as much protection as glass but at the cost of significantly increased weight does not seem that unbalancing -- although I have yet to really test it out on a character. My current light armor barbarian does not quite have the smithing skill yet to switch from furs/leathers to scale, but he is getting close.
Then I increased the weight of Dwemer armor and weapons a bit and dramatically increased the protection provided. At the same time, I reduced the weight of Orcish down to about the same as wolf armor, maybe slightly less and tweaked some of the damage/AR values slightly. So, now I have a medium armor in the light tree (scale) and a medium armor in the heavy tree (Orcish), either of which is suitable for mid game and can carry you all the way into late game if you have a character who identifies with those armors/weapons more than the more exotic glasses, ebonys, etc.
I think Requiem is just too hard for most players. I have heard a lot of players complain that they can't kill a bandit or a mudcrab, or they run straight to Bleak Falls Barrows and get creamed, or they put on a full suit of heavy armor without adequate skill or perks in heavy armor and find themselves drained of stamina and can't fight at all, or any number of similar scenarios. Then they decide the mod is unplayable.
Requiem has a bit of a learning curve. Once you know how the mod works, it is not that hard to kill bandits, wolves, mudcrabs, or even draugr at level 1, but you still can't just charge up and start hacking like in vanilla, you have got to be prepared and approach every combat situation tactically and strategically. I agree with you though, it is what Skyrim should have been and I wouldn't want to play Skyrim without it.
I am not familiar with immersive NPCs, are you meaning Interesting NPCs? I think that is compatible with the NRM patch. I don't use that mod myself though -- tried it and then decided I didn't need it and uninstalled it. Having extra free followers can make the game a lot easier though if you use them.