I sort more by fabric, once I know an item is colour-fast. So light-medium weight fabrics go together (on delicate), heavy things go together, sheets go together (especially flannelette, it sheds), towels are on their own because they shed. Anything that is unusually dirty or stained gets pre-treated.
I don't worry about "full" loads because I can set my water level. Everything gets a second spin on heavy duty to get the rest of the water out. Then I do fluff in the dryer (no heat) for a few minutes because they wrinkle a lot from that. After that it is air dry. Pants dry nicely if you have spare pant hangers - I put one hanger on each cuff with the crease in its proper place, hang them upside down, and they dry fast and don't wrinkle.
When I was in an apartment for a while (communal coin-operated machines) I did full loads, didn't do the extra spin so I didn't need the dryer, and just accepted that things would take longer to dry. Racks and shower curtain rods are our friends.
If you are worried things won't come clean in cold water, choose your detergent carefully and let them soak. Our day-time electricity is expensive, so I often start a load early in the morning, let it agitate (lid propped open a bit so it doesn't spin) then it sits all day. I restart it once the price goes down, and it is fine. In the apartment I was still paying extra if I used hot water (each apartment had its own hot water tank) so I would put laundry into a bucket, add detergent and water and let it soak, and then just dump the whole thing into the machine.