It wouldn't make much of a difference but I think it makes the timing more logical and consistent.

So, as I was thinking about how some categories of similar timing use milliseconds and other don't, I feel like it doesn't make sense for these categories that are still in the double digit length to have milliseconds timing since second barriers can realistically be broken. A solution that I've seen other leaderboards use is having it so milliseconds are only used for runs that tie to the same second, which seems like a pretty good idea to me, but I want to hear what y'all think.

Sure.

You want to jump towards something you can crouch jump onto and then at the peak of your jump, press the crouch button twice in quick succession. If you timed it correctly, you'll be able to jump higher than normal.

NSS has the same strats as all worlds, it's just that the autoscrollers are excluded. I think chatter's working on an all worlds tutorial which is a bit more updated than sam's tutorial so you can also use that as a guide whenever it comes out. :)

If it's your first run that is more than 1 hour, I would really not recommend 100% because of how daunting it is. I would probably recommend a category like all worlds, spongebob rta, or no scrolling sections since they are all more manageable and shorter than 100% (100% is 4 hours and the other categories mentioned are less than 3).

However, if you still want to do 100%, the route is basically all sleepy seeds + snooze z routing, but at the end you have to grind for snooze z's since even if you collect as many as you can throughout the worlds, you still wont have enough to buy everything in the shop. The best level to grind in is SSP. I believe the resources tab provides a guide of where the sleepy seeds are.