random spawn for multible objects

Here is a simple script that will spawn a random enemy from an array of enemies, in a random position defined by min and max positions (a square area), while making sure it doesn't spawn too close to the last spawned enemy, but does not check the area it will spawn.

 using System.Collections;
 using UnityEngine;
 
 public class EnemySpawner : MonoBehaviour
 {
     //Array of enemies to spawn
     public GameObject[] enemy;
 
     //Enemies will be spawned in random positions inside these boundaries
     //The minimum x and z position to spawn the enemies 
     public Vector2 minSpawnPos;
     //The maximum x and z position to spawn the enemies 
     public Vector2 maxSpawnPos;
 
     //The y position to spawn the enemies
     public float ySpawnPos = 1;
     //The time between enemy spawns
     public float spawnRate = 3f;
     //The minimum distance to spawn the last spawned enemy
     public float minSpawnDistance = 2f;
 
     Vector3 lastSpawnPosition;
     float lastSpawn;
 
     private void Update()
     {
         //Time check to see if it's time to spawn a new enemy
         if (lastSpawn + spawnRate < Time.time)
         {
             SpawnEnemy();
         }
     }
     private void SpawnEnemy()
     {
         Vector3 spawnPosition;
         //Selects a random enemy to spawn from the array of enemies
         int enemySpawnIndex = Random.Range(0, enemy.Length);
 
         //Will keep on generating a new spawn position until it's far enough away from the last one
         do
         {
             spawnPosition = new Vector3(Random.Range(minSpawnPos.x, maxSpawnPos.x), ySpawnPos, Random.Range(minSpawnPos.y, maxSpawnPos.y));
         } while (Vector3.Distance(spawnPosition, lastSpawnPosition) < minSpawnDistance);
 
         //Spawns a new instance of an enemy
         GameObject instance = Instantiate(enemy[enemySpawnIndex], spawnPosition, Quaternion.identity);
 
         //"Resets" the spawn timer
         lastSpawn = Time.time;
         //Sets this enemies position as the last spawned enemy
         lastSpawnPosition = spawnPosition;
     }
 }

Obviously this was a hastily made script that does most of what you ask, but hopefully this helps anyways ^w^