Treetop is the preferred map for SnS for a more consistent opening.
Here the Z-Sigil won't affect the set or weapon used.
The best weapon for this fight is probably the Divine Galatine. Theoretically a Thunder Evo would deal more damage but the para especially with the combination with the Z-Sigil give galatine the edge. Very Long makes the head very hard to hit consistently thats why most runners tend to use long.
Sigil 1: [ SnS Up 15 | Beam Slash | Element 12 ]
Sigil 2: [ Element 15 | Element 15 | Element 15 ]
Sigil 3: [ Element 15 | Element 15 | Element 15 ] or [ Element 15 | Duration 12 | Wait Time 17 ]
SW is very hard to play in this fight because of the twerk move. Rush Up makes it possible to avoid it more consistently and lets you play more aggressive therefore outperforming the other skill options for that slot.
You have enough time to take the Thunder Attack Fruit, All Elemental Drug and the Affinity Drink in the Arena since Narga's nuke takes some time to start. After PD'ing the intro take the SW Potion.
Narga's opening is the hardest one to get perfect. The fastest way to get both Obscurity stacks is PD'ing the first AND last hit of his nuke, that way his next attack will be the quick tail whip that you can PD for your second stack. Hitting the first PD is the important one. If you miss the last, he will do the fog into jump instead which you can PD for your second stack but its slower than the first option.
This is the hardest move to avoid correctly especially with SW. Without rush up you need to be full stamina otherwise it will be impossible to avoid completely. It will also require an animation cancel.
Evade slash -> hop -> upslash cancel -> evade slash
You could also do: hop -> upslash cancel -> evade slash for the initial tail hits. He will also most likely turn around after his jump so use an adv. Slash to gain super armor through his turnaround if you're close to him.
Since SW doesn't allow you to block the rain your only option without Rush Up is to run outside the initial circle and roll into it right when it stops. If you have rush up you can block it and try to get as many PD's as possible. With PD(Lg) this would even be more dps if you pd the last instance but I need more testing to see if you can run it on Lg or not.
Just a small tip for this move. Evade slash right as he dashes behind you so you can do an upslash while turning and evade slash his jump again. This way the timing is consistent and you'll avoid any windpressure that could possibly hit you at the start of the dash.