Kat.. How tall/long is your Arrowhead?
It'd be better if you planted Arrowhead on the outer side, and an upright plant in the center.
Otherwise, mature Arrowhead will cover and smother smaller plants in the center.

If your Arrowhead is young, it's probably standing straight, but will eventually spread, unless staked.

I have a combo, variegated Philodenron 'center' with pink and green Arrowhead/Syngonium along the edge of pot.

Center plant should always be taller.
Plants need be compatible when potting together.

Do you intend on potting Rosary Vine and String of Pearls in the same container?

Perhaps, others have better suggestions. Toni

either growing rosary vine and string of pearls in same container or in separate ones and putting it in one larger one.. hmm have to think about this.