I used to have a URL prefix property only, now that I have registered the domain property, should I delete the URL prefix one?
Most probably, no. It does not hurt to keep the URL prefix property alongside the domain property. And since you have created the prefix property before the domain one, it will have more historical data. The domain property will only start collecting data from the moment you have created it, it won't show the historical data that the URL prefix had collected previously. Here is an example of a domain I purchased recently: the former owner registered the https:// URL prefix property before registering the domain property. You can see the domain property misses any historical data before the end of October 2022. You definitely want to keep the URL prefix property here!