What template should I use?

[DuckMannnn]

Since my OC Nightwalker will be AKOF-styled, what template should I use?

[Sir Ghostler]

Kung Fu Man.

 

There are no SNK styled templates and most of the others that are available are poorly coded. You'd be better off starting with KFM as a base. Once you've settled in and really started coding, look at the code of the characters who utilize the style you want for reference when incorporating it into your own character.

[EndercreeperMugen]

As said above, it's best to use Kung Fu Man for your base. It can be a hassle to remove things you don't need (Leftover moves and sprites for example), but it's still one of the easiest ways to start a character.