Courageous was a Baltic large light cruiser, not a normal battlecruiser

Can Courageous and Glorious be treated as ordinary battlecruiser designs outside Fisher's Baltic plan?

No; they were specialized large light cruisers built for the Baltic concept, much smaller than Tiger and too lightly armed for long-range battlecruiser gunnery.

The class is an aberration tied to Fisher's Baltic operational scheme, not the next step after Tiger or Renown. At roughly 10,000 tons less than Tiger, Courageous and Glorious do not continue the Royal Navy's normal growth in battlecruiser size and fighting power. Calling them battlecruisers obscures their inadequate ranging battery and the shortened 18-inch weapons fitted to Furious. Their design logic sits closer to a very large light or heavy cruiser built for a special mission than to a capital ship intended for long-range fleet gunnery. The later comparison with the Deutschland class reinforces that cruiser identity: large hulls and heavy guns alone do not make either design a battleship or battlecruiser.