Okay, good.
I'm going to stress again that curing has more to do with salt concentration than anything. You can cure with no nitrate/nitrite whatsoever but you cannot cure without salt.
Curing salt is used more for distinctive color and flavor in the types of items you are doing and in the method you plan on using to smoke and the way you plan on using the meats, more than any other reason. Though it does extend shelf life by slowing spoilage and fat rancidification, cured meats of this type (the type that will be smoked then cooked again for serving--bacon also falls into this category--or the type that will be cooked completely then served hot, or will be cooked completely then chilled and, say, sliced for sandwich meat--turkey, turkey breast, possibly pork loin or fresh ham can fall into this category as well) do not require the same level of curing salt because botulism, frankly, isn't a concern, both because it is rare in these instances but, more importantly, because the food will either be cooked again at high temps or will be chilled quickly after cooking and will be maintained cold. (Note that this does not hold true if one is cold smoking, although C. bot is unlikely in or on otherwise unadulterated meat.) For sausage (adulterated meat) and meats being cured to dramatically extend shelf life or for shelf stability, a higher concentration of curing salt is used (especially for sausage), and/or a higher concentration of salt (especially for hams).
(The other thing that aids in shelf stability, bacteriostasis or bacteria kill--lack of water activity, i.e., dryness, as one employs for jerky and some sausages--is another technique that I'm not getting into here.)
Imo, a key element (other than the curing issue) is salt, and here I am speaking of flavor. Insufficient salt, especially in a curing brine, often makes the food taste more like it was brined in a 'regular' brine, i.e., it is not quite salty enough. One need not go over-the-top of course, but I find it easiest and, to me, get better results if I use a somewhat substantial amount of salt in the brine and then soak the item in cold water after curing (and rinsing) to remove some of the excess salt--a common post-curing technique with a number of foods.
For sausages and the base for dry cure mixes I am anal and measure amounts of everything by weight precisely. For brine cures I don't so much. I use 2.25-4.24 T pink salt/gallon of water (the range depends on what I am doing but, at just over 2 oz, even the high amount is much lower than recipes based on amounts like those in the OP. For salt, I use a pound; sugar, either none or up to a pound, depending on the finish I am looking for.
Does this make sense?
4 days is likely sufficient for both though this depends on temps and thickeness. You can go longer (and will need to) if your temps are on the cold side, that long or a bit shorter if you plan to inject.
