Personally, NVMP has rotted my perspective of Fallout New Vegas to the point where I cannot play it normally, I've played for 3 years so I can attest to the Buggyness, lagginess, and Jankyiness of the mod, THIS MOD! is not 100% Perfect, it is being currently developed by like I think 1-2 Man team over 7ish years, and you're probably wondering can I do [Blank] and most likely yes I'll say what im expecting you to say
Can you do Co-op? Yes.
Can you do Other mods but NVMP? Yes.
Can you do the entire game? Yes.
Can you Do The Frontier/TTW/New California etc? Yes
Can I Use Epic Games version? No It's doesn't work
Do I need all DLC? Co-op No, RADD Yes.
is the Quest Sync? No.
Will there be Desync? Sometimes Yes.

Basically to inform you before you do all this and expect a godly experience you will be either disappointed or intrigued depending on what you do with the mod and how you use it. But if you do enjoy a Co-op or MMO experience this mod might be for you. for me the main reason i come back is the Community as it is a cesspit at times but I've enjoyed the experience making friends & enemies within the Public Server over the course of my time playing NVMP

NVMP Discord (https://discord.gg/CbMqYKEPbF)

And if you have any questions you can ask in the comment's i'll try to answer them as fast as i notice them

Installation is a 5-10 Minute process although it can be hit or miss with anyone, issues can arise while installing if you find any issues installing and need support, please go to the NVMP Discord and ask for help in the support channel, but be patient as the support questions are mainly answered by Support Staff & Players
You can find the installation Below
https://wiki.nv-mp.com/en/getting-started (Recommended)
https://nuwiki.nv-mp.com/wiki/Getting_Started
(Note: The First Link says there's an automatic installer, there isn't anymore)
don't worry you can still play normal NV just don't use the launcher
Required:
A Steam or GOG Copy of FNV
a Discord account
Epic Games account (For Authorization)

But Basically
Step 1. Have a Fresh Install of NV
Step 2. Make sure it works
Step 3. Install 4GB Patcher, NVSE, NVAC (This will make your game crash less)
Step 5. Use LOOT to fix the Load Order (Not needed but highly recommended, there could be issues)
Step 6. Install NVMP launcher (Install from the First link)
Step 7. Done.

afterward, open the launcher it will ask you to link with Discord then Epic Games and boom you're in

Ring a Ding Ding or RADD. is the public server, This is what NVMP mainly revolves around,
RADD adds a bunch of MMO-like aspects to FNV including
Player led Factions
In-game currency (we all know caps would be useless)
New Content
Custom Areas
PVP
Reworked Weapons & Perks
etc.
It's still FNV just with MMO-like aspects that you can choose to participate in, that and quests are pretty bugged since a random person can just enter the same cell and bug out the area by killing all NPC As I said I can't explain the best But I have a guide which I've spent more time on that explains the gist
https://docs.google.com/presentation/d/1lX-uTqgF6FruxnS6QGYITQ-ckwheZRmP3VRGBNYyr7o/edit?usp=sharing

To play on the server it's required to be in the NVMP discord

And here is a video that shows you what RADD Combat is mostly like

Now most of you may be wondering, how is the Co-op experience, I will not sugarcoat it, there are multiple ways you can do Co-op within NVMP
each varying in different performances from what I know it can be extremely buggy, crashy, and downright ♥♥♥♥♥♥. if not set up correctly depending on what mods you use it can alter the performance greatly,
The options are limited and impractical for a perfect experience.
(Note: I have never set up a Co-op server except for using the WGS Bot)

Option 1. Port Forwarding
This is a complicated setup as you're allowing traffic through your PC's port for access this one is more for people who understand it a bit Im not too sure but this option is free and is dependent on set-up, and performance can vary
Option 2. WGS(White Glove Society) Patreon Server BOT
This option has the best connection, and stability but cannot be modded and has limited options as it's hosted on a server, although you can only choose to have TTW, Dust, Or DLC enabled, this option does cost money as you need to be subscribed to the NVMP Patreon for access which is a 10$ minimum (this is just for hosting, anyone that joins doesn't need WGS).
Option 3. Radmin/Hamachi
These apps and ones similar to it are used for a easier version of port fowarding as you're letting them handle it for you but similar to port forwarding. How you set-up the server will change the performance, Oh and it's free to use

From what I know servers can only have 5 players minimum.

(Edit: I forgor option 3 existed so I added it srry)