Back on my desktop, lots here to unpack
Good to know but how will a drop tube help if the powder is compressed anyways?
Black powder will "settle" from vibration or a drop tube. Compression is mechanical crushing of the powder granules. In drop tubing, the grains generally settle about as far as they'll go and that last little bit of compression doesn't damage the granules nearly as much.
What is your opinion of FF powder vs Pyrodex?
Just say NO to Pyrodex for this use, for any gun you care about. Pressure curves are far different that black powder, fouling is abrasive and harder, and it's far more corrosive than any black ever thought of being. Every gun I've seen ruined was shot with "only Pyrodex" cleaned, oiled and then stored. To really get all the corrosiveness out you have to clean multiple times. With real black powder, you need only clean once, dry and oil. I use Windex in my competition muskets and have no issues. The water in Windex cuts the fouling, the ammonia is a base that neutralizes the acidic residue, and the alcohol aids in drying. I can clean my competition musket in 5 minutes and it still shoots 2moa. The best use I've found for Pyrodex is killing moles in my lawn. Pour some in their little holes, add fuse, a match and fun times.
I assume bullet fit is like smokeless cast bullets that are .001" over the slugged bore. Traditionalists probably like lube but do others use powder coating? Would bullet casts consider bullet bhn as well by varying the tin mix and possibly adding lead with antinomy
Bullet fit is a variable. It depends on rifling type, depth, lead alloy, etc, BUT there are a few generalities. First, pure or nearly pure lead and by nearly pure, no antimony, maybe 2-4% tin. Alloy is important as black powder causes obturation on firing. If the bullet alloy is too hard, the bullet will not upset to perfectly fit the bore. Size depends on rifling and bore, in general though .001-2 over bore size. Weight is very important. Lube is absolutely necessary to keep fouling soft and under control. Powder coating will not substitute for lube on black powder rounds no matter what you're read on smokeless forums, it simply won't help. And before you even think it, yes, I tried it, with and without lube.
From the comments you've made, you need to forget what you know about smokeless reloading. Most of it simply doesn't apply. Start from scratch. Hang out on the Shiloh and BPCR forums to learn how those guys are making 1k yd shots with black powder cartridge rifles and I'll give you one hint, it ain't with Pyrodex nor powder coating. Those in the running for the top 10% are having velocity deviation on the order of 5 (or less) feet per second from shot to shot, verified by chronograph. I think they may be on to something.