I contain my mints in very large containers sunk in the ground. Remove most of the bottom of a container - leaving about a 2"piece at the outer edges (keeps container from collasping - then sink the container in the ground leaving the entire rim above ground. Fill with soil and add your root ball at the same level it is in its current pot. What this means is the soil surface you see now in the current pot is the same one you want to see when your mints rootball is planted in the new container. Water at a slow trickle and fill in around the rootball as needed.
When outdoor soil is workable enough that the container can be sunk in the ground move your mint outside and it will improve. Clip the long strand just above a set of leaves so it is inside the container rim. Keep any strands clipped so they remain within the rim of the container. This not only encourages branching of the strands it stops the mint from
growing over the side of the container and rooting in the ground. Pineapple mint is a stunning visual plant. I try to plant my mints where they get full morning sun and some afternoon partial shade especially when the mint is varigated. Do pay attention that the containers are getting enough water.
Indoors now: The strand can be clipped back now, you want three or four sets of leaves remaining, or pinch back the top set of leaves. Trim or pinch back to the next set of leaves. Set the pot in the brightest light available.