Hello
So, for Minecraft I suggest playing with keyboard and mouse, for second Forge is not a mod it's a mot loader, so you can use it to load your mod, That's simple, Download forge for the version you want, and launch it, don't touch anything just click install or something like this, If you got an error, launch the game with the version you want to mod, after this do Windows+R on your keyboard and type %appdata% then go in .minecraft then go to the mods folder, here you can drop all your mods, but be prudent when you download mods.. For the minecraft hacks clients he just need to download the hack client and put it in the version folder (Only if it's a hack client, if it's a hack mod, drop it in mods)
Plugins are only for servers, so if you want to open a server you'll need knowledge.. so I won't explain now. But when you will join a server, the owner of the server can put any plugins he wants no downloads for you but when you will join for exemple they will ask you to do /register password password and when you will come back, it will say do /login password
And for GTA V tbh I didn't really moded this game so I can't suggest; but if I need to choose keyboard and mouse or controller, I'd choose controller, It's more easy to play gta v with controller than keyboard, but that's my mind, you can try by yourself,
I am sorry for my bad english. I hope Im helpfull
-Official Forge link:
https://files.minecraftforge.net/