If you're new to slinging, don't chase the crack too much - even if you get your sling design perfect, without good technique you won't get a crack. It'll come with time as you refine your technique. However, the reverse is also true - with good technique and good sling design, you can get a crack with very little effort(so don't try to muscle it, that won't help) - I've gotten a solid crack as low as 35mph, which believe me it's hard to even throw that slowly.

What you want is a perfectly neutral release - your wrist not pronated or supinated too much. And there's the rub: "too much" is different for every slinger/technique/sling for many reasons. Pan Slings recently published a great video about spin control, which is caused by the same factors. To get a good crack, you want a good straight rifling spin. https://www.youtube.com/watch?v=idp6OjwG1I0

Onto your actual questions though - I went through this myself last year and winnowed it down to a couple of main factors(with tons of little details if you're interested): https://slinging.org/forum/YaBB.pl?num=1736654504

How much does your sling weigh overall? A multi-strand twisted cracker is probably far too heavy for a single-strand paracord sling. For light slings you need your cracker to be quite a bit lighter than your cordage. I've had the best luck with 90lb polyester micro paracord because the braid is tight, it's incredibly flexible, and it's fully round so it will create the traveling loop needed for a crack equally in any orientation(flat crackers are no good because they only twist in one plane and sometimes that doesn't line up with the loop coming down the release cord).

Anyways, with that 90lb paracord I can get a crack even from a 16g 4mm dyneema-only sling with a no effort throw: https://www.amazon.com/Micro-90-Cord-Paracord-Strength/dp/B01B1Y48FG I know the listing says it's nylon, but it's wrong the nylon version is the 95lb stuff that has a twisted core like normal paracord and is a little thicker. In-person it's a lot easier to tell, the feel of the material is completely different. If you already have nylon though, that'll work fine too - I've found the difference is only 10-15%(very subjectively) between that at the polyester version.

You'll want 4-5 inches of loose cord on your cracker, with a simple overhand knot to prevent fraying too much and then 2-3 inches of tassel. Best attachment is something aligned with the direction of the release cord, I prefer a common whipping(see my other thread).

One thing to keep in mind: you're not going to get that .308 crack you hear from the balearic guys out of a light single-strand sling, there's just not enough weight. This will be more akin to a .22 crack, but it will still be very loud and quite satisfying. If you want a heavier crack, you need a heavier cracker, which requires a heavier sling to get enough mass moving to crack it. Some of those really loud balearic slings are 80-100g. But in my experience you can still get a real big crack out of anything >30g if it's very flexible and you have an even taper and good cracker. My Pan Sling is about 38g and cracks like a monster. And Neandrthal has said his slings come out about 48g and those almost get a balearic-sized crack.