keep in mind that pellets and sabots and primers are designed to remove money from YOUR pocket. When I first got into muzzleloading in the 1970's, you could shoot all day and still only spend a dollar or two. Pellets are convenient and like all convenience, has a price. I am a traditional fan and use only Holy Black. However, in your in-line, I'd suggest loose triple 7. A powder measure is cheap. And there are what seems like 100's of various machinations of sabots, concical, and composite bullets for in-lines. Again, all with a price. There are now some molds out there for folks to roll their own.
I assume you will do some target shooting and then go out for deer. Keep in mind that your gun may be built to withstand elephant loads and buffalo loads, you are hunting white tail. You do NOT need a load capable of crushing granite or buffalo skulls. You most likely won't be shooting deer at 400yds. Flatter shooting of a light weight short bullet doesn't necessarily mean more range. Keep your loads in the 70 to 80 grain range, and a bullet about 300 grains and you will still get slapped abit by the recoil and you can kill buffalo if ya need to. (Trple 7 runs about 15% "hotter" than holy black) Back around the 1850's, the British War Dept experts discovered that a longer bullet and less powder extend range better than a short bullet and more powder. This is due to a number of factors including air resistance and flight stability. An 80 grain load of trip 7 with a 300 grain bullet would be similar to the 1870's 45-90 Buffalo cartridge.
I think Loggy has experimented with some of those all lead molded bullets in his in-lines, and may have more insight into them.