Even if your volume was going down, the C910 would likely bring you frustrations on things you take for granted on the Ricoh production machine. If you've liked the machine during your five or however many years with it, then I'd be inclined to stick with the brand and workflow you're used to.
There is an envelope adapter for running them flaps closed that is currently in beta testing. As of March '21 there was no official announcement or launch date. If all goes well I would guess that availability could be later this year.
Sorry but that's all I know.
Sustainable Printing Goes
Far Beyond Using FSC Certified
or Recycled Paper
This informative paper on deinking: demand, principles, problems and solutions also explains why printing technologies are not all equally compatible with paper recycling systems; and why just a small fraction of printed material in the paper can cause difficulties. Link To White Paper