I don't think it's necessary to create a dedicated group. You could do it this way:
- Create a function that spawn your enemies.
- Inside the function you insert several ifs divided according to the score range you want. For example: If points is >= 0 and < 100 then spaw enemy A, if points is >= 100 and < 200 then spaw enemy type between enemy A and enemy B etc.
By doing this, by calling the spawn function of the enemies once, you can create enemies automatically based on the current score.