Best way to get controllers and keyboard input ?

I made this script using the XInput plugin for Unity :

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using XInputDotNetPure;
 public class PlayersInputManager : MonoBehaviour {
 
     private GameManager gm;
     private GamePadState[] state = new GamePadState[4];
     private PlayerIndex[] playerIndex = new PlayerIndex[4];
     private bool buffer;
     // Use this for initialization
     void Start () {
         gm = GetComponent<GameManager>();
         for (int i = 0; i < 4; i++)
         {
             playerIndex[i] = (PlayerIndex)(i);
         }
     }
 
     private void Update()
     {
         if (buffer) { GetInput(gm.buffer1); buffer = false; gm.inputs = gm.buffer1; gm.prevInputs = gm.buffer2; } else { GetInput(gm.buffer2); buffer = true; gm.inputs = gm.buffer2; gm.prevInputs = gm.buffer1; }
     }
 
     void GetInput(PlayerControls[] p) {
 
         for (int i = 0; i < 4; i++)
         {
             state[i] = GamePad.GetState(playerIndex[i]);
 
             if (state[i].IsConnected)
             {
                 p[i].horizontal = state[i].ThumbSticks.Left.X;
                 p[i].vertical = state[i].ThumbSticks.Left.Y;
 
                 if (state[i].Buttons.Start == ButtonState.Pressed) { p[i].start = true; if (i == 3) { gm.keyboard = false; } } else { p[i].start = false; }
                 if (state[i].Buttons.LeftShoulder == ButtonState.Pressed) { p[i].jump = true; } else { p[i].jump = false; }
                 if (state[i].Buttons.RightShoulder == ButtonState.Pressed) { p[i].interact = true; } else { p[i].interact = false; }
                 if (state[i].Buttons.LeftStick == ButtonState.Pressed) { p[i].boost = true; } else { p[i].boost = false; }
 
                 if (state[i].Buttons.A == ButtonState.Pressed) { p[i].down = true; } else { p[i].down = false; }
                 if (state[i].Buttons.B == ButtonState.Pressed) { p[i].right = true; } else { p[i].right = false; }
                 if (state[i].Buttons.Y == ButtonState.Pressed) { p[i].up = true; } else { p[i].up = false; }
                 if (state[i].Buttons.X == ButtonState.Pressed) { p[i].left = true; } else { p[i].left = false; }
 
                 if (gm.vibrations) { GamePad.SetVibration(playerIndex[i], gm.vibration[i], gm.vibration[i]); }
             }
         }
 
         if (Input.GetKeyDown(gm.start)) { gm.keyboard = true; }
 
         if (gm.keyboard)
         {
             if (Input.GetKey(gm.moveleft)) { p[3].horizontal = -1f; }
             else if (Input.GetKey(gm.moveright)) { p[3].horizontal = 1f; }else { p[3].horizontal = 0; }
 
             if (Input.GetKey(gm.movedown)) { p[3].vertical = -1f; }
             else if (Input.GetKey(gm.moveup)) { p[3].vertical = 1f; } else { p[3].vertical = 0; }
 
             if (Input.GetKey(gm.shootdown)) { p[3].down = true; } else { p[3].down = false; }
             if (Input.GetKey(gm.shootup)) { p[3].up = true; } else { p[3].up = false; }
             if (Input.GetKey(gm.shootleft)) { p[3].left = true; } else { p[3].left = false; }
             if (Input.GetKey(gm.shootright)) { p[3].right = true; } else { p[3].right = false; }
 
             if (Input.GetKey(gm.take)) { p[3].interact = true; } else { p[3].interact = false; }
             if (Input.GetKey(gm.boost)) { p[3].boost = true; } else { p[3].boost = false; }
             if (Input.GetKey(gm.jump)) { p[3].jump = true; } else { p[3].jump = false; }
             if (Input.GetKey(gm.start)) { p[3].start = true; } else { p[3].start = false; }
         }
     }
 }
 

But I don't think it's the most optimized way to do it
I made that buffers system to make my own "ButtonDown" and "ButtonUp" functions
The Input Manager of Unity is really broken when you plug and unplug controllers, that's why I wanted to make my own system