Here's a rabbeting bit and a mortising bit. Rabbets are rarely wider than the thickness of the piece you're glueing into it. The rabbiting bit has a bottom mounted bearing you let ride against the edge of the wood. You can get them with several diameter bearings and change them out. Using an edge guide and the mortising bit, you take a scrap of the material and lay it on edge where you want the rabbet. Use it to scribe a short line on each side of the piece you want to rabbet. Lay a straight edge (the factory edge on a half inch piece of MDF for example) from scribe mark to scribe mark. Your mortising bit's bearing will roll on that edge.
Plywood is not 3/4 inch thick anymore, it is not 18mm, slightly thinner. So your bit should go no deeper than about half that thickness. You can see that a 3/4 diameter mortising bit will remove the entire rabbet area just fine.
Dados and grooves are another matter. You can buy an 23/32nds plywood bit just for that purpose, but there is no guarantee that any particular piece of plywood is exactly that thickness. So for a dado or groove, you are much better off using a half inch bit as suggested and an exact width dado jig as in the video. They are pretty easy to make. Here's a drawing.
You fit a piece of the material that will go into the dado or groove between the two horizontal boards and use the star knobs to cinch tem down. Clamp the jig securely in palce and begin to do the routing. A half inch straight bit will work but I'd go right back to a half inch mortising bit for this. The top mounted bearing will ride on the side of the rails as you slide the router first one way, then the other. One important feature of mortising bits is that they cut a really flat bottom groove, rabbet or dado.
The more I do, the less I accomplish.