Ok so
Yes and no
Having more Pokemon does Technically increase your egg amount in some cases.
For your first question the answer is yes. Five sprigatito and one ditto would just give you the same amount of eggs as one ditto and one sprigatito. Because the ditto would only be able to bread with one sprigatito at a time.
Your second question also has the exact same result. The third on the other hand will definitely give you the most because each sprigatito and fuecoco would be able to bread separately.
5 sprigatito + 1 ditto = baseline amount
5 ditto + 1 sprigatito = baseline amount
3 fuecoco + 3 sprigatito = highest amount possible.
Also each fuecoco could pare with each sprigatito multiple times so you could get up to 9 eggs
Source: experience
Alright so I was scrolling through my wall and I saw a post by ditto asking if I was almost done with the eggs. I had completely forgotten! So I decided to get on it before I got replaced by a ditto.
So first I had five ditto breed with one sprigatito for 10 minutes, with a level two egg power. It gave me nine eggs…
Next I tried flipping it around. And I got similar results.
Finally I tried three (F) sprigatito with three (M) fuecoco. I got a whooping 25 eggs in ten minutes.
So yeah I would definitely recommend the last one.
Sorry I took so long. I hope this answers your question.