First you need to figure out which african cichlids you want. There are Malawis,tanganyikans, and Victorians. Since you listed yellow labs and electric blues those are malawis. Now within malawi there are mbuna(rock dwelling cichlids like yellow labs), haps (open water species like elctric blues) and peacocks(very similar to haps but not as large.
The general rule is you can mix haps and peacocks but mbuna need to stay with mbuna. You could do a very nice all male hap/peacock tank. If that's what you want.
If you want mbuna then I suggest Ps. Acei and rusties along with the labs a good starter species. In a tank that size you have A LOT of stocking options. I would check out the intenet or lfs to figure out what you like and we can help you from there with stocking.
For more info about mbuna here's an article:
Link
AS far as filtration I don't know a whole lot about wet/dry filters so I'm not sure. It sounds like you're fine. Malawis don't need a lot of flow but my mbuna love playing the current.
Keeping plants with mbuna will be difficult. They love salad!
For Ph they like it on the higher side a Ph of near 8 is usually the goal. I keep mine at 8.2 It's better to be stable than fluctuating. Using some crushed coral in the filter or decorating with limestone/texas holey rock can help buffer your Ph.
