Robert
I can answer about Pix4D. If you're already using Pix4D for processing drone imagery, most if not all of the resulting outputs are all compatible with the imagery capabilities of ArcGIS - that includes ArcGIS Pro, ArcGIS Online, and ArcGIS Earth. (I'm assuming you're not using ArcGIS Enterprise or Image Server but the same is true).
I said "most" outputs because in some cases it will depend on the format - e.g. if you want to use the point cloud, output a *.LAS file...
Note if you're not already using Pix4D, we have options for drone processing as well. Drone2Map is generally equivalent to Pix4D for field/office use on a laptop, and Site Scan is our cloud-based (SaaS) offering. These include direct connections for publishing results in ArcGIS Online.
Cody B.