Just thought I'd share my basic guide for NiCO here. I still need to do more thorough testing, however I feel like I know the character well enough to give you a general idea with regard to how she works and what your gameplan should be . Since NiCO is a new character, there may be some incorrect information. Don't hesitate to point out any mistakes.
Gameplan
NiCO's gameplan is to play the stun-launch game. You want to really make use out of her 9-11-13 strike speed and be offensive in the neutral game. NiCO is generally safe on block. This makes her, in addition to her small movelist, a very forgiving and easy to pick up and play character. Her most damaging juggle generally is PPP[P] and you'll get this even at fairly low launch height. Even though NiCO stun game is above average, you won’t get better juggles from launching from a deep stun, at least in terms of damage. So it’s always a solid idea to go for stun-launch or stun-throw. Mix these two up to remain as unpredictable as possible.
Neutral Game
NiCO’s neutral game is really good. Your opponent really has to respect your 11f 6P string which has several mixups. Learn the mixups of the 6P string, it’s her best string honestly. You can also start opening people up with CH 3KK which gives an excellent stun, is safe on block and the second kick tracks. Be careful though as a smart player will duck it on reaction. She only has 3KK and 3K2K which is a high-low mixup so both options can be avoided by ducking. That’s why I only suggest using it in stun, not on block. Her basic punch string isn’t as good as her 6P string but you can use it as a string to interrupt slow strings of your opponent. PPP gives a decent stun on CH but unsafe on block, so be careful with it. PPK is awesome and the final kick can be delayed by a ton.
NiCO’s main downfall is her lack of tracking. Makes sense since she is a safe character. Linear moves and safety go hand in hand, that’s why Kokoro is so safe as well. In neutral you should definitely make use out of your tracking moves to beat sidestep-heavy opponents. 4P tracks and is a great stun opener, though it is somewhat slower than 6P. 4PK is a full string which is very useful. Both strikes track and the kick ender is an awesome wall splat. It’s also only -6 on block. 6KK is super dope too. Only -2 on block and the second kick tracks. It gives enough frame advantage on hit to keep the stun game going. 6KK into 6P+K is a good setup since 6P+K crumple stuns and is quick on impact.
Spacing and Whiff Punishment
NiCO’s range isn’t amazing, though it also isn’t as abysmal as Honoka’s range so that’s a plus. As a general rule of thumb you want to be in your opponent’s face but if for some reason your opponent is zoning well and you can’t get close, she has a few tools at her disposal. The most important one at range I would say is 4H+K. Reaches pretty far but, most importantly, crushes all high strikes and I believe even some mids. Unsafe on block but has a low kick followup. The followup has lots of room for delay, so use this to your advantage. Another good tool to close distance or whiff punish is 236P or 236[P]. The range is deceptively long and out-prioritizes a lot of moves. Also great as a wall splat. Then finally 9PP is a good string to close the gap quickly. Gives a nice stun on CH as well and is safe on block.
For whiff punishment, 6H+K can avoid both mid and low wake up kicks if timed correctly. 1P is a very quick high crush and stops pressure from characters like Phase 4 or Rig. 4H+K is also used as a whiff punishment tool and so is 236P / 236[P]. 66K beats low wake up kicks but is unsafe on block.
Combo Game
NiCO doesn't seem to have much in terms of combos. Her moveset is very limited in that sense.
Stuns and Stun extenders: NiCO's stun game is awesome. Her main strength is her arsenal of crumple stuns which can create a lot of 50-50's between launchers and throws. Good moves that get the stun game going are 4PP, 4H+K, 6P string on CH, 3KK on CH, 6KK on CH and 9PP on CH. Her best extenders in my opinion are 4P+K, 6P+K, 7K (leads into Fatal Stun), H+K, 3P or even just her basic P. This leads us into the next part of combos: launchers.
Launchers: Her launchers are good. She has launchers at different hit levels so her mixup potential and stun-launch game is solid. 8K (high kick), 9K (mid kick) 3P+K (mid punch) and 3[P+K] (charged mid punch) are her main launchers. 66K (mid kick) also launches if the opponent is is a deep stun. 8PP causes a bound on CH.
Relaunchers/Juggles: NiCO is fairly limited in terms of juggles. 66K seems to be her most reliable juggle and you can use it twice after a critical stun level 3 launcher. Other juggles I found useful are PPP and KP. 9K and 9P also work in some scenarios. 8PP can also be used as a juggle and causes a bound which has a few follow-ups.
Enders: In general, you can only use NiCO's charged strings as enders only if you didn't use a juggle in your combo. So PPP[P], PPP[P+K] and 6PPP[P] only connect after using them straight after a launcher. When using juggles such as 66K or KP, end with PPPK, PPPP+K, 6PPPP, 6PPK, KKK or 6KKK. After the 8PP bound end the combo with close hit 236P (hard version) or 236K (easy version).
Wall combos: After a hard wall splat, your universal wall combo is 8PP - 236P. Make sure to charge the 236P slightly for a little bit of extra damage and to guaranteee you get the close hit. If you have 1 meter, you can also go for 8PP - 6S or 8PP - 6SH - juggle. That's entirely up to you.
I haven't really looked at environmental combos yet but her BnB seems to be 66K juggle into any of her enders described above. 8PP - 236P is a consistent one as well.
Matchups
As a general rule of thumb, NiCO does really well against slow grappler characters like Bass as they 1) don’t have the speed to interrupt her strings and 2) don’t have the best defensive tools for dealing with her pressure. She also does well against a character like Rig who relies a lot on high strikes for pressure because she has access to crushes like 4H+K, 3H+KK and 1P. Her worst matchup is probably Christie. Very evasive with her Jakheiho stance; NiCO barely has options to counter her since her tracking is so bad. Marie Rose is another tough matchup because MR has her special sidestep Minuet to deal with NiCO. Plus it’s very dangerous to be aggressive against MR since her expert holds hurt, like a ton.