break in brood cycle with split walk away Vs Q-cell

[windfall]

How long a break in the brood cycle is required to help control v-mites?
We were planning to split off a nuc or two mid-july to overwinter. Being new we were originally planning on buying a queen or ripe cell (assuming we have no capped Q-cells when we perform the split)
But we also love the simplicity and self reliance of doing a walk-away split and allowing the bees to do their thing. I understand this adds 3-4 week of time over a new queen, but provides a much more significant break in brood over the queen cell option. We would also like to increase the number of hives with the genetics we already have rather than bring in something new (for now).
I think we could do the split sooner by that margin if I steal resources from two hives instead of one. The 8 frame nucs we started with this year are up to 16-20 frames each
We are running no treatment with bees bred by Kirk Webster toward that goal. So staying ahead of mite populations is going to be paramount, as well as having nucs to restore those losses which are normal (and those caused by being new!)

[caticind]

I use walk-away splits to create brood breaks as part of varroa management.

The only real trick: Time the split to coincide with your local dearth.  There are generally plenty of drones around still, to get your new queen mated, but a break in brood here (plus sugar dusting during the period without larvae, if you do that) not only helps reduce varroa load but also reduces the amount of stores used during the dearth.

Where I am, in NC, this means we do splits around June 20 or first week of July.  Many experienced keepers in my county club have said this was crazy.  But they said that about foundationless too...  So far, we've had absolutely no trouble with hives getting built up for winter.  This might not work as well for you if you don't have at least a small fall flow, but could be worth a shot.