FOR YOUR OWN SAFETY, STEP AWAY FROM THE CHECKBOOK!
Howdy
Please, get to a couple of matches before you spend any more money. The rules can be difficult to understand when read dry. They make a lot more sense in context.
A couple of years ago the categories underwent some major revisions, and I still don't completely understand them, but your Bisley Blackhawks do not limit you to the B Western category. You can use pistols with adjustable sights in any age based category, such as Wrangler, Forty-Niner, Senior, Silver Senior, and Elder Statesmen. The idea behind B Western is flashy clothes, as often seen in B Western movies, drop style or Buscadero holsters, and rifles made in 1880 or later. That means no 1860 Henry, 1866 Winchester, or Winchester 1873. Most of the time in the B Western movies, the most common rifle seen was a Winchester Model 1892, so that what was what the originators of the category originally intended. The recent appearance of replicas of the 1883 Colt/Burgess rifle has somewhat muddied this.
You might want to hold off on ordering a bazillion 45 Colt cases too.
These days, the go to caliber is 38 Special. Not just for cost, but because with lightly loaded 38s recoil is greatly reduced, so fast repeat shots are easier. It may not be very historically accurate, but that is the direction most of the competition has gone. I wish I had a dollar for every CAS shooter who just had to have a 45, but later jumped on the bandwagon of trying to get the 45 Colt to recoil like a lightly loaded 38. The grand old 45 does not perform very well like that. There is also a brisk trade in cowboys dumping their 45 Colts for 38s.
Whether or not you want to shoot heavy loads, at least try a bunch of guns before you sign the check. If you show up at a match, and show a reasonable amount of interest, shooters will lining up to allow you to try their guns.
Regarding 44-40, dunno where you heard it is more time consuming to load than 45 Colt. Yes, 44-40 can be a little bit fussy to load, fussier than the 45 Colt, but it does not take a whole lot more time to load. Where 44-40 really shines is as a rifle round used for Black Powder. Because of the slightly thinner brass at the neck, 44-40 expands better to seal the chamber than a 45 Colt does at relatively low pressure, keeping all the fouling in the barrel where it belongs.