Creating various enemies with various movement for Space Invaders game

I’m currently working on a top-down space invaders game. I finally figured out how to make enemies come down the screen using Victris Game’s object spawner. But now I have other issues:

-making enemies appear on a timer (because the object spawner is set to create enemies periodically)

-giving the enemies various movement patterns

I couldn’t find any tutorials built around these specific issues. Any suggestions?