I want to get latest x number of posts but only 2 from a single category. Is it possible through query posts. I can do that using posts loop anyway but would like to know if its possible through query posts method.
WordPress Query Posts for 10 latest posts only 2 per category
Have a look at the function reference and write your own function to get what you need.
It should work four you to query the posts from specific categories and merge them together into an array. Afterwards call the function in your template.
Also check the following Post.
UPDATE
It is currently not possible to query the different types in on statement. Better would be to organize your posts. Have a look at Taxonomies