Yield

I'm planning on growing 8 plants DWC, 4 white widow and 4 AK47. I have 2(2by4) t5, 8 bulb 436 Watt fixtures for the plants to flower under. I'm going to veg both for 2 weeks under 1 T5 2*4 fixture, then flower under other two fixtures for 8 weeks. Grow room is 8*5 what kind of yield can I expect.

Too much room for the light, you will need to partition it off so your lights don't spread uselessly. I would make two 4x4 rooms and have 4 in each. This would let you flower at two different times so you only need to wait 4 weeks per harvest or so.

If you wanted you could do the room as it is, but it's stretching the range of the lights a bit

And yield is really up to you, how long do you want to veg, how much height do you have, how much time, etc. Id say 1oz a plant bare min, with tops around 4 oz a plant without getting too crazy.