Yes, there is an original-style expansion valve next to the firewall. I tried to show a glimpse of it in the video. It is new (which means nothing these days); from Classic Auto Air. I have a similar new one and I experimented with it today. It seems to flow freely at ambient temperature (92 degrees today) when I blow through it. It is my understanding that it closes when the tube gets cold. If it was stuck closed, I assume that would cause vacuum on the low pressure side. Not sure what the high pressure would do under those conditions.

You still need a pressure switch on the low side if you originally had an RV2. Some of the high side switches are high pressure only, some are double acting as high pressures and loss of charge, but it has to really lose all the charge before it shuts down the compressor. With no switch on the low side, if you had a partial leak and its on the low side and it's pulling a vaccum on the low side, with no low pressure switch, it's just sucking atmosphere in and contaminating the system. The low side switch is also your defrost control, and your compressor capacity control.
You can test your expansion valves with some nitrogen, not hooked up and in your hand, it should have little restriction.