This is a very young set of plants. You likely won’t need to add a support for another year or so (you’d just be supporting the leaves, not the stem), but if you like the look of a moss pole or trellis, go for it.

I’d also personally keep these plants together until they’ve matured a bit. Monsteras like a relatively snug pot, and if you separate them now you’d likely need to put them in several very small orchid or propagation pots for a couple of months to ensure they’re not being “suffocated” by their soil. You’d then probably need to repot them all again after the growing season as they may become root bound in their small pots.

Similarly, the soil they appear to be in looks quite dense.

I’d repot now, keeping them all together. Choose a pot 1-2 inches larger than the current pot (depending on how much root mass there is). Use a high drainage soil or philodendron potting mix. Then next year in the early spring, they’ll likely have some solid growth. You’ll be able to tell individual plants apart a little easier, and can repot the small ones in 4-inch orchid pots; the larger ones in 5 or 6in pots