+atk/-spd or +res/-atk Halloween Nowi?

Id ignore her but thats because I dont like her. If you were to choose one pick the first ivs and give her a bladetome. Or the second iv if you have the motivation/resources to use fortify hone fliers

Why don't you build Aversa instead, both need a bladetome to reach their max potential anyway, and Aversa's prf has a much better effect compared to Nowi's.
I would consider Nowi to be better than Aversa if she had +spd -res as this way she would have better offensive spread, and -res is the best bane because lowering her res won't change much for her while a -def or -hp will make it almost impossible to take a hit on her def.
Also Aversa has a better bulk than Nowi

OOF Whose Ivs really hurt...
I would use the first one,but since you probably gonne use Aversa (Shes more a summer Tana,though),i would save her for trading if it comes one day...
I would love some mergs for Halloween Nono!

It might sound funny but H!Nowi is great thanks to her prf in flier team, her great mobility helped me a tons of times. I know that her tome's skill flier formation is present in SS but it's still nice option to have, not to mention she has hone fliers and live for bounty, firts skill makes her great support for flier emblem, second gives you more crystals for lvl ups so she is worth using despite those ivs.
I have 2 copies one is -atk +def and +hp -spd, i chose -atk one and have 2 goad fliers to bump her atk and spd by 4 points (add ally support and she has +6 to atk and spd ). But you might prefer +atk - spd to use her bond skill and have QR for SS or b slot to make her into magical tank with a bit of support.