Yes, it is possible to draft against specific ADP, pre-draft rankings, and expert rankings.
When you are on the Draft Simulator's Draft Settings page, scroll down to the Draft Against section. Here you can select whether you want to draft against expert rankings, a variety of ADP sources, and/or pre-draft rankings. You can select any combination of ADP sources and pre-draft rankings you want to draft against.
You can toggle on/off the "All Experts" option depending on whether or not you want to draft against a random set of expert rankings.
New for 2020, you can draft against the rankings of FantasyPros Experts Dan Harris, Mike Tagliere, and Kyle Yates.