The following is based on my experience with them. I'm only commenting on those I've used.
NC (North China) - dense 2 Band with gel tips. Available in normal or chubby form which is a a shorter knot.
Leader Silvertip - dense 3 band with marginally treated tips. Very soft with less backbone than the NC
Captain 3 Band - Dense thick hair with treated tips. More scrubby than the NC variant.
Silk HMW - thin hair that is reasonably densely packed. Only very mildly treated. Same as Oumo Silk HMW variant. Incredibly soft without the gel tip feeling.
Foregoer - their most expensive knot. All natural - no treatment. Very soft and thin. I really like this knot. Very soft when dry and wet. I'd describe this as true silvertip of the best quality.