Trail Boss is so bulky that you cannot put enough of it in a case that you will generate a dangerous pressure unless you compress it significantly. I have never loaded with Trail Boss since I can accomplish the same effect typically more inexpensively and certainly more cleanly with the traditional fast-burning shotgun/pistol powders. Trail Boss rarely achieves anywhere near full pressure for a case. Lower pressure leads to less complete combustion and more fouling, and higher pressure leads to more complete combustion and less fouling. The "super clean" powders are nearly always faster than the "standard" powders (e.g. Hodgdon Clays vs. Alliant Unique) and generate more pressure for a given level of performance. Shooting Clays vs. Unique is the same deal (Clays is much faster, which is why it's so clean), as is using full-pressure loads of 2400 in a .30-06 (using previously published Alliant data) instead of reduced loads of slower powders such as H4895.
The one advantage I see in Trail Boss is that you can easily use it to create a reduced load in a cartridge for which there is no reduced load data out there using faster powders- simply figure out how much fills up the case with the bullet seated and start at 80% of that. I shoot old and popular cartridges such as .30-06 and .44 Magnum, for which there are tons of verified safe reduced loads out there using other powders, so I can use a bunch of different powders for reduced loads. But let's say you have an obscure round like a .36 Nosler where you want to dial it back to plink with 9.3 mm Makarov bullets and there is of course no load data available for that. Filling the case up with Trail Boss is your only safe option unless you want to pay a bunch of money to get a lab to pressure test loads with fast-burning powders for you.
Accuracy very much depends on the particular firearm, bullet, and most importantly, shooter. The biggest detriment to accuracy other than a shooter who flinches is a bullet that is too small in diameter for the barrel, or a bullet that is too short/light or too heavy/long to stabilize with the barrel's twist rate and it's velocity. My '06 doesn't shoot lead bullets less than 150 grains well at all due to its twist rate, ditto with my .44 Magnum SRH not shooting 0.429" bullets very well due to its bore diameter being a smidge larger than that.