I'm taking the opinion that as our market continues to be successful and grow, I want to give back to the investment so that if there is a correction, applicants are more drawn to my property in contrast to competitors.

There are companies who do this but I find they're competitors who do this on the side and the upcharge is substantial.I recommend that you do a lot of research on what furnishings/design get you the greater ROI in that market and start there. 

One of our local competitors has only a 4-page contract.

It might be a good idea to analyze the reviews of your exact competitors to understand common themes and demographics.Shannon 

They use code injections to pump their listings to the top, use meta-deranging, and funnel jacking on competitors—these are techniques nobody else besides Sonder uses.

I think they are a new competitor to AirDNA.

They are absolutely the most likely to tell your competitors what and when you bid.Second many investors are using the same strategy you are using.  

This will allow you the flexibility to try out niche keywords while still going after the $$$ keywords.In the secondary campaign make sure to create unique ad copy to the keyword it pertains to.Try to create demand in your ad copy by offering an incentive that is better or unique to one of your competitors in the paid Google search ad space.  

And I would see what type of marketing they are doing and how their rates compare to competitors. 

Build a table of rental rates by size by competitor in the area., D.