The remote is IR, but it has a fairly wide field and a relatively powerful emitter. I typically have it on the table next to my chair pointing in the direction of the system and it works fine.
The remotes are the same. The difference is that the Vivaldi Upsampler doesn’t have functionality for receiving transport commands for Mosaic via IR. Rossini, Bartók, and Vivaldi One all do. There is a mundane technical reason for Vivaldi not having this functionality right now.