I found a directional answer to the questions on what topics pay more ad revenue.
I don't know if this has been discussed previously, likely it has since this is a very active forum but I couldn't find a posting on this. Apologies (please don't ban me
if repeated else where.....I'm still trying to find my way around here ).
There is a tool called Google AdWords - Keyword Tool which is targeted at those who use Adwords to place Adsense ads (so its meant for the person paying for the ad, not for the person who is receiving ad revenue).
It will show you for any word or phrase several things including the relative amount of competition amongst advertisers for different key words or phrases, the relative search volume the prior month and on average.
My take (no link provided as I'm not sure I can do that yet in this forum) is that from a publisher perspective, use key words that are highly competitive from an advertiser's perspective and that has a relatively high search volume vs other key words.
Am I reading that right?