It probably would be best to repot it. They usually come that way. It may droop a little after repotting, some do that as they may be in shock due to new home, new pot etc. You want no more than 1 inch or so between outside of rootball and inside of pot, so yeah only go up one size. It will grow as high was you let it. Some put in hanging pots and let them hang or climb curtain rods etc.
They will climb just about anything. Use a well draining potting soil and a pot that has holes in bottom with a tray to catch excess. Just remember to drain the excess.
Most houseplants are killed by overwatering. You have bought one of the easiest to grow. Feed it a light fertilizer every 3 months and it give it lots of light, keep the soil somewhat moist but not wet and it should stay happy. These also grow very well in offices with flourescent lighting. I have seen these vines be 30+ feet.

Has anyone ever had Devil's Ivy climb on its own? I just got one and was told that it would need to be tied up if I wanted it to have an upward structure.

Sometimes they will hang onto a rough surface, like a pole covered with bark, but generally they need some help by being tied to the pole. I use green velcro garden tape.

Diss, I don't know of any Pothos that grows vertically without support.
VT, your Devil's Ivy (Pothos) requires some type of pole to grow upright. I find bark works best..Toni

Well I actually had one climb my bathroom wall on it's own, the bathroom has real rough texture (almost like tree bark) I had it sitting on my counter and 2 of the vines that were curled up by the wall just began to curve up they grew up quite a ways before I figured out they was digging into my wall, it left almost like small rust stains on my wall where the plant was digging in when I went to remove them from the wall, but the leaves that were on those two vines were about 3 times the size of the rest that were hanging down, so pretty, but I didn't want it to destroy my walls.