I tend to start with a long sound then trim it down to a hit rather than the other way round.
The best way to explore is to forget it's a drum synth and treat it like a synth.
Also get a rough sound and just switch through the wave types, constantly triggering from the unit itself and from a velocity transmitting source. Even sequence with different velocity hits.
Sometimes I will make an entire kit using just one wave, forcing me to push other sections in directions I'd not normally go.
I couldn't say I have any fm tips per se as it's just another type of synthesis but defo playing with the spectra is key, take it to max and min and cycle through, again though I'll try to make a longer sound first to evaluate what's happening over time and then trim that down, often playing chromatically rather than changing pitch on the unit. Then see where it takes you. Make sure the noise and click aren't getting in the way by using the section mute function often to really isolate what you are doing, pure genius from Nord on that!
I also don't pay much attention to keeping the 'kick' on channel 1etc, it's easy to switch sounds later but I prefer changing kits maybe on the last quarter of a fourth bar and since the sounds are wildly different it makes an interesting fill! With a little planning you can really get some great effects happening, especially if a tail is not cut with another trigger.
Defo make longer sounds first, go for an fm pad or bass with a tail and then shorten the envelope, either manually or with velocity.
Biggest problem I have with the ND2 and ND1 is programming a kit without making a track at the same time!
Now I've learned to build the kit as a track and not worry about it, I don't attempt either exclusively anymore, they are so easy and quick to edit.
I can't imagine any of that being any help but it's made my stomach tingle thinking about those little wedges of Swedish delight!
Pity the ND3 looks like a load of old codswallop!