If I have three different adverts running for an adgroup that are all prefoming well with similar CTRs, should I let all three continue to run or pick the best one and see if I can't try and improve a little more with more variation testing? Is there any negative effects of having three different adverts continuously running?
Depends on how many click and impressions you have. If you don't have a lot of data your decision to pause one or create another will be skewed. If they all have similar CTRs look at your conversion rate and CPA. Even if your CTR was really high on one ad and low on another you still want to look at the conversion factors because would you rather have an ad that gets clicked on a lot and costs you money and it doesn't convert or have an ad that has less of a CTR but the users who click on that ad convert for a low CPA.