I have just used retargeting lists in RTP using RTP segments.
So I have a segment of people that have visited a particular page on my site. I then go to the retargeting tab and create a new segmented audience. I then send the audience to Google Analytics where I create a new audience definition. See this page for set up - Personalized Remarketing in Google - Marketo Docs - Product Docs
I then use the audience I set up in Google Analytics as an remarketing audience in Adwords.
Not sure if that helps but that's what I have done so far with it.