Which Nowi?

Mine is -spd +def. My old one was +atk -res. I think you should take the +atk.

Hello, take the - hp + def with the - hp Nowi can be more fragil and the + def can help here a lot, and don’t worry the skills that you had on your Nowi + speed - atk will always be there if you merge one Nowi into the other and well she will not even have to learn the skills ;)

I'd say the +Def one, but of course depends on your build too. +Atk one is good for doing the Vantage thing but otherwise +Def or +Res would be better. When you merge your old 5* to the new one the skills are transferred as well so don't worry about those.

Personally I like speedy Nowi. I'm using my original +spd -res nowi until I can get a -hp, but with speed boon she avoids a lot of doubles, which increases her tankiness, and after a potential hone dragons or speed she can get quite fast. attack bane is unfortunate though, and actually HP is her best bane along with speed banes for folks who want to ditch her speed entirely, so either of your other two iv sets are actually quite good.

It all comes down to personal taste, for me +Def/-HP are my preferred IV’s for the basic Aether/Steady Breath/Guard/(c flexible depending on team)/Quick Riposte build

If you mostly tier 19-20 then Def is best stats with a bane spd or hp but preferably bane spd. If anything from tier 18 and below then spd is fine. Why? Mostly due to there being a lot high speed units in tier 20 that it just isnt worth investing into her medicore spd when you can max out her defensive as much as possible and run a breath skill with QR3