Speaking from a treatment point of view, The most effective time to treat with OAV is when there is the least amount of capped brood.
Don't over dose them, I believe multiple easy doses of OAV are more effective than blasting them. OAV is also honey safe.
The other methods are temp sensitive, strips, gel or pads, I think that these are harder on the bees. Use with care.
As soon as your queen starts laying they are committed and will not leave.