Play many sounds (60 to 200) without Unity cutting sound

This seems like a scenario where you could make good use of Update() vs. LateUpdate() timing.

You can keep a global controller around to listen for enemies to report their deaths, then play pre-mixed sounds accordingly based on the quantity.

First, an example script for the controller to listen for enemies dying:

 public class DeathWatch : MonoBehaviour
 {
     // Sets up a singleton that can be called via a static variable
     // It will create itself when requested if it doesn't already exist
     // And will assign itself if it already does
     private static DeathWatch sdInstance;
     public static DeathWatch instance
     {
         get
         {
             if(sdInstance == null)
             {
                 // Expensive, but only has to be performed only once
                 DeathWatch verify = FindObjectOfType<Deathwatch>();
                 if(verify == null)
                 {
                     GameObject newObj = new GameObject();
                     sdInstance = newObj.AddComponent<T>();
                 }
                 else
                 {
                     sdInstance = verify;
                 }
             }
             return sdInstance;
         }
     }

     void Awake()
     {
         sdInstance = this;
     deathReported = false;
         currentDeathCount = new Dictionary<string, int>();
     }

     // DeathWatch-specific from here down
     bool deathReported; // improves efficiency
     Dictionary<string, int> currentDeathCount;
     
     public void ReportDeath(string enemyType)
     {
         if(currentDeathCount.ContainsKey(enemyType))
         {
             currentDeathCount[enemyType]++;
         }
         else
         {
             currentDeathCount[enemyType] = 1;
         }
         deathReported = true;
     }
     
     void LateUpdate()
     {
         if(deathReported)
         {
             foreach(KeyValuePair<string, int> kvp in currentDeathCount)
             {
                 // Play sound based on the enemy type kvp.Key
                 // and death count kvp.Value
             }
             currentDeathCount.Clear();
             deathReported = false;
         }
     }
 }

Next, we have the simple adjustment to the enemy script to support this:

 void Update()
 {
     // Example death
     if(health <= 0)
     {
         Die();
     }
 }

 void Die()
 {
     DeathWatch.instance.ReportDeath(enemyTypeIdentifier);
     PlayDeathSequence();
 }

... Yep, it's basically two lines for the enemy units. One to provide an identifier (a string is just an example. You could use any type of value to identify them and adjust the Dictionary accordingly) and one to report their death for the current frame.

That said, if you intend to batch them within a small time window rather than same-frame only, you'll need a little bit more information (for instance, the integer portion of the Dictionary could be replaced with a class/struct for more detailed and grouped information as desired).

^{Edit: (Whoops, messed up a copy/paste and forgot to change a variable name)
Edit 2: (Fixed another simple script error)}