To get as much vertical speed from a wall jump as possible you have to hit it as soon as you touch the wall, in other words press the button during the buffer frames just before touching the wall. Starting a wall climb optimally is more tricky and I don't have an exact answer as to what the best possible timing is, but you want to start walljumping around halfway up the arc of a full jump.
D-00-03 in particular is really precise because you have to start with an awkwardly low jump but hit all the walljump timings so you build up enough speed to get up. I wouldn't recommend doing that strat in runs until you're going for seriously competitive times; it will kill runs and for a couple of seconds time save that's just not worth it.
The autosplitter doesn't know how to split when hitting an exit so you have to do the final split at the end of the last level manually. If you're already doing that then make sure you have exactly 125 splits. That's all I can think of, if you need more help you should ask on the community discord: https://discord.gg/d7MFhQh
Edit: I saw your run and the problem is indeed that you're not manually splitting on the last level. Unfortunately there's practically no way to get it to split there without access to the game's source code.
That option makes the game submit individual level scores when playing in episode mode. If you turn it off episode scores are still submitted unless you're in offline mode.
I haven't had this problem, nor have I heard of anyone else having it. The only thing I can think of suggesting is to check that your video card drivers are up to date. Our community discord (link in the relevant thread on this forum) has a #support channel for stuff like this, maybe someone will be able to help you there.
Splits only really matter when you're contesting world record, and even then if I can get them from your splits.io there's no problem there.
That's all there is, as long as you can run the game at 60fps with your selected graphics settings. Framerate drops make the game move slower.
In other words, turn Steam to offline mode before launching N++.
On intro, level view is allowed. There's not really a time difference so it's a matter of preference which one you want to play with. In row speedruns it's not smart to use level view because it goes column-wise, so you'd have to do a bunch of menuing after each episode.
I've now organized the categories into tabs similarly to the way they are in the game. I wanted to do this before but didn't realize it was possible (how to do this is very unobvious in the site UI), thanks for giving me a push to look into it ;P
No one has done co-op runs yet so there hasn't been need for leaderboards. If you have a category (or several) in mind, please explain them and I can add them.
N (v1.4) is one of the best for ILs. It has in-game leaderboards for highscore mode (which involves collecting gold) and there's a mod called Nreality which adds a speedrun mode (which is simply completing levels as fast as possible) and a lot of extra levels. In fact, because of the leaderboards and the game's extremely high skill cap most of the community is centered around IL highscoring. It's an old game and most levels are already fairly well optimized, but if you're interested, check out our forums at http://forum.droni.es/