If you only have 4 tradelines, you need to have only 1 reporting a balance for maximum score. # of accounts with a balance will ding you with 2, most likely and depending on algorithm.
Store cards are unpredictable and should be avoided if possible, as stated above. Personally I've experienced only partial gains with store cards as AZEO as opposed to a bankcard giving the full gain. Stated differently, the no revolving balance penalty seems to partially apply when using a storecard, whereas when using a bankcard, it doesn't apply.