Is there a difference between the protein found in red meat (like beef and ostrich) and white meat (like chicken and pork) and protein from fish and should you aim to get these in in any particular ratio to one another? Or could protein intake coming mostly from just one of these types be sufficient?
Realistically, protein is just protein. Certainly there are some minor differences in types of protein as there are differences in carbohydrates and fats as well. The primary difference in terms of digestion, however, is what you are getting with your protein.
Protein in fish contains a very small amount of fat compared red meat. It's difficult to take in the fat that the body needs without eating it in meats unless you want to upset another ratio of your diet (e.g. you could drink milk to increase fat, but would jump your carbohydrate intake as well).
The primary idea is that you would want to balance your ratios of protein, carbohydrates, and fats to suit the type of diet you are undertaking, but don't worry too much about the various types of protein.