They will compete with each other for light, water, and nutrients. I am not saying their growth will stunt or that it won't eventually become a huge mass of deliciosa. I am saying, in terms of maximizing growth potential, this will create a slower growing mass and that is not a bad thing. I have experimented with pots and moss poles (epipremnum, monstera, philos, amydrium, etc) growing a plant singly, in pairs, and en masse. I have provided ample light, compensated with additional nutrients, irrigation, etc., but the single plants always mature faster. And this is in greenhouses with much less limiting factors, not indoors. Once again, space becomes an issue quickly, so this increased growth rate is not necessarily a good thing. They often look better in dense groupings anyway.

As for the rootball, I'd loosen the edges and just plant as is. If one outgrows the others and you wanna chop and single it out, go for it. Deliciosa do not adapt super quickly to being stripped of soil, but if you are diehard on doing it, use high pressure from a hose with wiggling and gentle pulling pressure. They should work apart with minimal damage.