if you run two ads (in the same campaign and ad group) with the same keywords, do they both run simultanously? If so, does that mean you will receive more impressions if you were to run 2 identical ads simultaniously as opposed to just running one? If so (again), can you change the keyword bidding for a particular ad even though it is sharing keywords with other ads in that ad group?
Yes, but I believe that they will just alternate automatically No - if you run two ads at one time, you will not get double the impressions. They split it up. So if you get, say, 2000 impressions, 1000 will be with one ad, and 1000 will be with another. At least that's how I understand it. Someone please correct me if I'm wrong...
As said, if you have the ads set to rotate evenly (adgroup option) - then both the ads will receive roughly 50/50 impressions.