First, you'll need the SA Mod Loader: https://github.com/X-Hax/SA-Mod-Manager/releases
(Requires .NET 8 to be installed on your computer)

This tool will allow you to toggle and organize mods very easily, and download mods with just 1 click from sites that support it.
Just go to the "releases" tab, download the 32bits or 64bits version according your PC's specs, and run the installer, it should automatically detect your game and install the mod loader there for you.
(Be aware that Windows Defender might trigger a false positive with the Mod Loader, download from the main GitHub page is safe.)



After booting the loader for the first time, go to the Game Config tab, and turn on all the options in the patches section. These fixes several issues with the PC version of the game.



Oh, and be sure to use the One-Click install option when downloading mods, it saves you the hassle of manually putting them on your mods folder. If for whatever reason it doesn't work, place you rmods in your mods directory inside your Sonic Adventure 2 installation folder:

Congratulations! You've just set up the game and you're ready to start modding. Bellow I've divided everything into several categories:

-SA2 Render Fix: https://gamebanana.com/mods/452445
Fixes plenty on rendering issues, particularly with lightning and materials that are broken in the ports.

-Cutscene Revamp: https://gamebanana.com/mods/48872
Fixes many material and transparency issues with the cutscenes introduced by the GameCube port.

-Retranslated Story -COMPLETE- : https://gamebanana.com/mods/437858
The original english localization cut many details and subtleties from the plot, this changes the subtitles to be more accurate to the original japanese script. Remember to set the audio to japanese in the game's menu.

-HD GUI: SA2 Edition: https://gamebanana.com/mods/33171
Upscales several UI elements that looked too low res in vanilla.

-IMPRESSive: https://gamebanana.com/mods/469542
Changes the text font from Comic Sans back to Impress like in the Dreamcast release.

-Stage Atmosphere Tweaks: https://gamebanana.com/mods/407838
Edits lightning and fog to more closely match the Dreamcast version.
Be sure to place this mod at the bottom of your mod list, it can cause some problems otherwise.

-SA2 Volume Controls: https://gamebanana.com/mods/381193
Sound mixing was always an issue with SA2, but the ports broke it even more due to the lack of the Dreamcast's volume limiter.
This lets you change the music and SFX volume to what you find the best.

-Mech Sound Improvement: https://gamebanana.com/mods/412706
Fixes the mechs' SFX to be less ear piercing.

-SA2 Input Controls: https://gamebanana.com/mods/515637
Adds SDL2 support, allowing pretty much any controller to be used with SA2.
Also be sure to select this mod in the mod loader and click configure; scroll down and set the deadzone to 5%, as
the PC added a huge deadzone for no reason, making the game more clunky and twitchy than intended.

-Better Radar: https://gamebanana.com/mods/313161
The radar in the hunting stages was made les precise in SA2 to create artifficial difficulty, leading to many players
feeling frustrated. This mods reverts the radar back to how it was in SA1.

-HedgePanel - Sonic + Shadow Tweaks: https://gamebanana.com/mods/48950
Fixes small oddities with the speed characters.

-Sonic: New Tricks: https://gamebanana.com/mods/48941
The original game suffered from mapping all actions the same button, causing inputs to overlapp.
This lets you remap Sonic's actions to any of the four face buttons.

-Retranslated Hints: https://gamebanana.com/mods/350607
Some of the hits provided in the hunting stages are vague or flat-out incorrect due to poor localization.
This fixes them providing better context to what emerald shard or location they refer to.

Phew! That should be it, now you're ready to experience Sonic Adventure 2 as Chaos intended (?
I don´t think I need to state this, but just in case, I'm not the creator of any of these wonderful mods, I just compiled them in a single, comprehensive guide.

I'll try to keep this guide up to date, let me know if any mod gets outdated/replaced, or if I should add any!