it looks to be in coir dust (coir peat) - it falls off the roots very easily. so you can replant it into 2 pots with minimal root damage. I wouldn't split it into more pots then that - the stems won't branch, so you need several in a pot to look good.

make sure it does not dry up more then halfway. coir peat allows air to reach the roots even when it is very moist and it does not compact like peat. it rewets very easily too. if it were mine - i'd leave it for now in coir dust, but separate into 2 pots.

many nurseries converted to growing in pure coir dust by the way , even succulents.

it is a good mix for small pots for tropicals grown indoors.

you can reuse it too - that is it's possible usually when you unpot (it falls off the roots with ease). so you might want to add approx 1:1:1 small bark:large perlite: coir dust (that you have already from the pot).

It's not crowded. Growing several stems together like this gives your plant denser foliage overall. Separating them won't necessarily make them grow any better than they already are.

As for repotting, they don't mind having their roots disturbed one bit. Since these are somewhat epiphytic in nature, meaning they grow up the trunks of large trees, I mix in 50% Miracle Gro orchid bark with with a fast draining soil. Also, these are rainforest plants, they can tolerate drying out, but they prefer being watered quite frequently.

I agree, it doesn't look crowded. Mine is much older has like up to 6 stems in one pot, still don't look desirably dense.

It's better not to repot plants right after shipping, since they are already in a shock condition. You can up-pot it in a month, without disturbing roots, just adding missing soil. It's too young now for a bamboo pole, later it will need some support and maybe heavier pot, since Monsteras tend to become top-heavy fast.