Superspeedways, honestly, I find to be quite dull, but I'll help you out with some basics of what to change in the track.ini and why.
1. Hidden Values
Alright, for starters... the following values should be added to [ ai_track ] at the end of the default physics values (meaning before [ ai_track_gns ]). These are from Daytona06, and are why the AI there tends to have more lowlining and blocking than you normally see. Pretty much every track ever made for this game doesn't put these values in the track.ini (which I would imagine defaults them to zero), but they are valid.
ai_offset_long_lookahead = 5.0
ai_offset_lat_lookahead = 1.0
These values are probably fine, given that it's from another Daytona (and basically all Daytonas made for NR were based off the default one as far as I'm aware). I don't think there are any other hidden values that go in the track.ini, but I'll have to check that.
If you don't like what these do, put a semicolon in front of "ai" to disable them. This will mostly stop the kind of "conveyor belt" type racing (where everyone stays in a pack and just shuffles around meaninglessly) a superspeedway produces.
2. ai_dlongpad_scale
Alright, so there's the obvious; "make ai_drafting_distance smaller" refrain, but, honestly, anything lower than 1.2 for a superspeedway is going to create wrecks every other lap... probably.
Time to get to the fun stuff. Like ai_dlongpad_scale. This seems to control how early the AI set up a pass, and in what direction they tend to prefer to pass in. If that sounds like absolute madness, you're right. The closer this number is to 0, the later the AI will pull out to make a pass, and the more likely they are to stay behind a slower car, seemingly. A positive number will mean the AI generally looks to the left side to pass first, a negative number? Well, they'll think about making the right side work more often.
Most superspeedways should have this set to about 1000, which is absolute madness for anything other than a superspeedway. Stick a negative sign in front of the 1000 and see what happens. 8)
3. ai_dlat_pad and ai_squeeze_pcnt
Also known as the; "How are TM Master Cup series races good?" values. The former controls how closely the ai run side by side, with lower being closer. Turning this down by even small increments can have big results. You can make this a negative number if you want, and on some tracks, that's not a bad idea.
You can kind of do that with ai_squeeze_pcnt, but you don't want to do that here. This controls how far apart the min and maxrace lps are from each other. Increase this by... say, by 0.10.
Values here are very LP-dependent, so the same values on different tracks will do different things.
4. Disable ai_line_modifier
Put a semicolon before ai_line_modifier and that's all, but for ovals, you honestly might want to have this. Up to you, but I've seen the AI go for the outside a bit more often with this off. You'll want this disabled for road courses for obvious reasons.