are there any diferences betwen boxes in terms of how many seals i get ??? like master vs guru boxes

If you're new and you wanna check imperial seals rewards, i pretty much recommend you to check out alchemy here, imperial cooking rewards (besides the money itself) are pretty lame and time consuming, instead of trying to grind 10k seals to get a butcher knife you can get 2k alchemy ones and trade them for Magical shards and craft the knife yourself, faster and cheaper.
If you want milk, just use the byproducts for that unless you really REALLY need the cp.