I do not know what seat/room 3 is.
I haven't used Superliner coach for some years. Last time was on the CS Oakland to Van Nuys. There were two of us in wheelchairs, mine manual and the other power. One wheeler gets the window and the other gets the aisle. There are no trays for wheelchairs or the first row of seats near the wheelchairs. I think there was an electric socket but am not positive. Other seats in the downstairs section have trays like the upstairs coach seats.
Seats in that section didn't used to be assigned other than the two wheelchair spots. A wheelchair spot does not entitle the passenger to a companion spot (which would logically be in the first row behind the wheelchair spots, or facing them if the wheeler turns around). Often the wheelchair space fills with luggage despite signs to keep it clear for wheelchairs.
My chair is rigid, not folding, it used to be I could reserve a wheelchair coach seat and say I wanted to transfer so they would reserve both a spot for the chair and an adjoining seat. Now only folding chairs can reserve a transfer seat. This is a problem if you are traveling alone because the folding chair probably will not be within reach if you need it to go to the restroom.
If you are not a wheelchair user but have difficulty with stairs, then you could be in any of the downstairs seats (depending on where they start numbering the seats).
If you are traveling alone and will want food or beverage service, be sure to tell the coach attendant when you board, otherwise you may be trusting a stranger when you hand them your credit card with "Could you please bring me a hot dog from upstairs?"
