just some personal preferences:
1) i have no problem with different meats being stacked in the racks. Whatever juices drip down from the meats are all going to be good, and a little pork juice or grease isn't going to harm your brisket at all--it will make it better. i usually just do whatever fits best--it's all good :D
2) i still maintain that if you're putting a bbq rub on your meat, most liquids you put in your drip pan will not have a noticable impact on the meats' flavor. Plus i've cried a little inside everytime i've poured beer into a water pan
But there are many people who disagree with me, and i do not have the best taste buds in the world, so i say try it--worst thing that could happen is you'll waste some beer
3) this one i don't know about--i've never used an electric smoker before--i only use charcoal. but i would just follow the manual's instructions as to the best placing of the wood chips.
lastly, the most important element to BBQ is experiment!
never take what someone else says as the gospel truth. everyone has a different grilling/smoking setup, different climate conditions, different tastebuds, ect., ect., ect. i've learned more by doing precisely the opposite of what's considered "OK" in the bbq world than if i would have just accepted other people's 'rules'. And it's pretty hard to mess up bbq to the point of inedibility.
Have fun :D