I bought similar bag from Wal-mart, the lady in garden center told me, they are about the same height and size, just follow instruction on the bag (smaller variety in one bag, larger ones in one bage, they don't mix them together). She showed me a bag of lily (35 bulbs), they will be differnt in size, nothing to worry about that either, instruction gives mimnum distance between bulbs; some do not need so much space, plant it like it says anyway. How did your tulip come out? I'd assume although some tall, some short, they should be fine.

I am in Zone 5 and start all my dahlias in pots and I have good sized plants to put out in the garden at planting time.They bloom earlier, that way you can enjoy them in bloom longer.
The assorted varieties meaning,dinnerplates,decorative,cactus etc.They all grow the same height,just the flower size is different.