Trying without much luck to recreate the video wedging mosaic demoed by Scott Keating here
https://www.sidefx.com/products/pdg/ [www.sidefx.com]
For some peculiar reason the video is not directly linkable and there is no .hip file but it is halfway down the page in the AUTOMATE section, Wedging video.
I am trying to create the TOPs node graph in the attached but not sure what all the nodes are.

In the left column green box of course is a ROP geometry output , and in the right column red box there are 5 nodes.
#1 is ROP Fetch I think, #s 4 and 5 are Wait For All and I think FFMPEG Encode Video respectively.
But what are numbers 2 and 3 in the right column,
Generate_Contact_Sheet
Wait_for_Entire_Sequence ?

Also anyone know of a working example of TOPs based video mosaic for simulations?

It should be a partition by frame TOP. This will gather all renders that have the same frame in one workitem.