Welcome. My name is XXXXX XXXXX would be glad to assist.
As for the dryer electrical receptacle, it must be within 6 ft of the dryer location.
Other than that, there are no real requirements besides 30 amp #10 wire and 4 wires.
The plug connection can act as the disconnect as long as the dryer can be moved and not stationary. If not movable, it needs a disconnect switch.
On the vent, the service entrance main and meter must have standard clearances for working space. 36" in front for depth, 30" total in front of the equipment left to right.
All cables must be protected from physical damage.
With your description, it could be possible for an inspector to claim that the wiring isn't protected from the vent if that vent produces extreme heat that could do damage inside the meter and main.
The outside equipment is designed to withstand all the harsh environments and is very rugged.
Now, the local jurisdiction can have many amendments to the NEC and require much more than the standard.
Every area, be it a city,county,township etc., has their added code enforcement issues and it is only local to them.
That is why the NEC always states, the AHJ (Authority Having Jurisdiction) has the last say and final approval.
I would not install one near a vent for that reason alone, it isn't using the best judgment but as far as the NEC, I find nothing there related.
Also, all equipment must be installed per the manufacturer guidelines.
So, the furnace install may be more of an issue for inspection than the electrical portion.
You must also keep in mind, that the areas utility companies, gas and electric can have rules that must be adhered to also.
If you have something else specific you want more information on, please reply.