All the broody hens that i have used to hatch have been top-ranking hens - that's a pre-cursor to how i have done things in the past. I have let the broody sit in a nest, no separation and no interference from me. I never had an issue with other hens laying in the nest, nor the broody being bullied off a nest or harassed in any way. After the hatch, I've removed the broody and chicks to ground level - sometimes in a wire crate (with food and water), and left the door to the crate open so momma can take the chicks out, if she so wishes, or keep them in the coop. After 2-3 days, momma always seemed to be happy to take the chicks out all day, but never stray far from the coop - at that time I would put the wire crate just outside the coop, for the chicks to eat and drink (and return the crate to the coop before dusk, so momma returned with the chicks before the rest of the flock). Depending on the hen, I would find the crate empty at around 6 weeks, and find her and the chicks roosting with the rest of the flock. Time to remove the crate and let them do their thing.
What i have learned is to trust a mother hen to make decisions - they rarely get it wrong
I'm merely sharing my experience and in no way suggesting it is how you should do things. Our set ups, climate, flock dynamics and personal preferences are all important variables.
One thing I would say is that having two broody hens at the same time can make things a bit dicey, once chicks are hatched. I have read that some mother hens can kill chicks from the other's hatch. Thorough planning would be necessary to keep both mothers and their chicks separate, whilst remaining with the main flock (helps integration of chicks and maintains the mommas' hierarchy within the flock). It's not something I would personally do, I'd break one of the broodies and then let just one bird hatch chicks at any one time.
Good luck with the hatch