Here is a PDF to help diagnose a deadout -
https://nybeewellness.org/wp-content/uploads/2014/04/winter_deadout_key_2-24-14_final_draft-2.pdf
An unchecked mite population can overwhelm a colony in a very short period of time. Mite populations can triple every brood cycle.
The situation is so dire 95% of colony failures can be attributed to the mite. You can no longer keep bees like your grandpa did.
I am convinced genetics is the answer, buy local survivor stock queens, test and treat as needed to keep mite levels below 3%.
You want queens produced from known overwinter survivor colonies, not mass produced poorly mated queens and migratory bees.
All of the great BeeKs profess that your best queen is one your surviving colony(s) made by your selection.
The following is the easy stuff and nothing is written in stone, So much depends on location.
But keeping your mite level at less than 3% (by whatever method) is critical to colony survival.
And the only way to know is a mite wash, just looking at the bottom board is not enough.
Everyone freaks about killing bees, but in the bee world the individual is disposable, the colony is the organism you are saving.
A strong colony will not miss a half a cup of bees, a sugar shake is the alternative but not as accurate, and accuracy is critical when the target number is so low.
While honey is drying humidity is crazy, some will have problems some won't. Some space the lid with coins (it doesn't take much), sticks, drill holes, Vivaldi boards, quilts, burlap, etc.
Once the honey is capped the hive can be closed down, some stuff screen boards, some switch boards to solid, upper venting is limited so the bees can propolize it closed as needed.
I highly recommend 2" of foam insulation minimum on the lid to prevent condensation. A piece of plywood leaned up against the front of the hive at an angle will block wind and drifting snow from the entrance.
There are lots more things that can be done.
As long ago as before the advent of removable frames, bees have been kept in a cellar over-winter.
The other big part is what will fit with your methods, how much effort can you spare.
Stacking hives is beneficial, one BeeK stacks multiple hives in a cluster and wraps them up, they all share the heat.
NUC boxes stacked next to each other, the clusters will hug the shared wall. Double screen boards can be used to separate stacked colonies so they can share heat.
Don't give them more space than they need, this means you have to monitor them to prevent early swarming coming out of winter.
Don't over feed them, they will fill every cell in the box with syrup, no room for brood.
I don't like the wide open aspect of a screened bottom, it does not take much of an upper opening to create a chiminy effect and change the air in the hive.
Opening the whole bottom is too much, it's a gulp when the girls need a sip.
I don't have a hive beetle problem in my area so I'm leaning towards a morning sun afternoon shade setup to keep the boxes from over-heating, an insulated lid helps here as well.