The 10 gallon tank will house a baby corn or king for a year or so. Adults do well in the 20 gallon long tanks. I have my corns in 20 gallon longs. They need a warm side an cool side (although couple of mine don't have extra heat since we keep our house in the 70's - 80 most of the year an are doing great.

Most snakes like something to hide in to feel secure. I've used paper towel rolls, cut down boxes. Pretty much anything. I have a honduran milk that love being under newspaper. I use newspaper / paper towels for substrate. Its cheap an works for me.

I've had king snakes in the past an will not have another one. A baby managed to escape (how I don't know because I had that lid SECURE) found him outside dead.

Another king I had pooed / musked on me everytime I handled him. Couldn't take it anymore an re-homed him.

Have fun! Oh, an by the way...snakes are addicting.