>I'll be running all 8-frame mediums, foundationless, starting with a 5 frame nuc that is HBBBH, where H =honey and B=brood. I need to get in my head a plan so I'm thinking hiving them as HEBBBEEH where E=empty frame.
That's a good plan early on. It doesn't break up the brood nest and keeping brood warm is an issue early in the spring. Later you can add some empty ones to the middle of the brood nest.
>When adding second med box, should I move the frames of honey up, replacing them with empty frames?
Yes. that or add the box to the bottom.
> Or is it better to move up one or two frames of brood, assuming they've drawn out an empty frame or two and started brood in them)?
It's a judgment call that depends on how warm the nights are and how many bees there are to cover the brood. The safer bet is to move the honey up, but it does incite them to move up when there is brood and enough bees to cover it.
>Also appreciate tips on the timing of this: e.g. waiting until one (or two) empty frame is drawn or both drawn and has brood?
I'm more worried about the density of bees than the number of combs. You need to be able to make a gap in the brood nest and it's quickly filled with festooning bees. That would indicate a surplus of bees available to cover the brood.