For shirt types .. Yes. As long as the exact same image (same size, same location) is being printed, it doesn’t matter if all of the garments are not the same style.
The price you pay per garment is determined by the total number of units sharing that design.
Note that different colors of garments may require different ink colors.
For shirt sizes, you can mix and match sizes in whatever way you need to in order to complete your order. The main thing to keep in mind is that the design we print will need to be sized to accommodate your smallest garment.