As a Merchant Culture, I use "Power Investor" to earn money by investing in a resource deposit, please display an info popup above the best investment in each empire.  I'm going to spend two or three minutes hovering over each deposit anyways to find the best investment, so can we have a Quality Of Life improvement and just get the best one above each empire, including our own?

We should still see the best investment per empire and not just one over the best one in the world, because we may want to invest in our own resource or an ally's resource instead of a neutral/enemy's, even if the neutral/enemy investment would give us more money.

Totally agree with this, unless when playing in the fastest paces, the Affinity Action should feel a bit more thoughtfull than just building/investing for the sake of using the option.

Yes, I'm going crazy checking each resource tile just in case it offers 10k money instead of 5k. (there was a 10k resource at the start of the era)

Agreed, and also maybe show similarly which "best territory" for the Cultural Blitz ability of the Aesthete cultures gets the most influence. 

I was just thinking about this last night. It would be nice and save us some time.