You can mix and match any and all of the 28mm plastics currently on the market. Some go slightly better with others in terms of styling, but they are all essentially interchangeable, subject to a little bit of fiddling around with the neck joint one way or another... I thought I saw this explained in an answer to your previous question about 'which figures should I buy?'
If you look at my Game of Thrones Westeros thread on the main fantasy board, you'll see I've taken components from at least a dozen different sets from at least 6 different manufacturers and smooshed them together. And I don't think you'll really be able to tell much difference in the finished figure
