The difference between 20 and 50 round boxes of ammo is how many are in the box. That's it, that's all. All of it is 44 mag ammo loaded to 44 mag specifications. All factory ammo is held within the limits set by SAAMI and enforced by company lawyers. If a company makes a gun and labels it as a 44 mag than it can shoot any 44 mag ammo within the SAAMI limits. It doesn't matter if it's a revolver, lever rifle, desert eagle, or anything else. Any ammo from any of the major manufacturers is going to conform to SAAMI specs.
Some companies (garret and buffalo bore come to mind) load slightly hotter loads but I have no idea what pressure these are loaded to. The vast majority of firearms manufacturers will tell you not to use this ammo as that is what their lawyers will advise them for liability. Most US made firearms will be able to handle it but it's up to you if you use it or not.
Whether hard cast, FMJ, soft point, hollow point, or anything else doesn't matter. All that matters is that it isn't pointed. I'd want the flat to be at least the size of the primer of the round in front of it but that's just me. I do shoot quite a few of the Hornady Leverevolution bullets which are pointed but have a rubber tip and are safe for levers.
Some bullets are a little too lightly constructed and can over expand or fracture at rifle velocities due to the longer barrel. That only really matters at very close range since 44 mag looses velocity so quickly and of course only matters if you're hunting. Targets wont tell the difference.