Green Orb Result

That Fae is the best thing you can ask for, dream IV i've been searching for years so merge it. Also +spd nowi and fae are basically a meme build in the end, can help in PvE but not PvP (arena).
Special spiral Lilina is pretty good, but so is a Wo dao zelgius with quickened pulse and Ostian pulse. But lewyn is pretty good with it too, and even some other units. it's a new skill so if you want to be sure it's better to wait more.

For Fae I'd go with +DEF/-HP, because I don't feel like middling speeds are really worth any consideration for SPD IVs.

For Lewyn, if you don't have a use for him otherwise, a Lilina with Special Spiral can be pretty destructive.

Lewyn is a top tier unit in my opinion, as the combination of Forseti, Special Siral, and the Flashing Blade Seal make him a absolut monster.
In my opinion, foddering him as your only copie to Lilina is only good when you really love Lilina, and want to +10 merge her.

For Fae:
What IV depends all on what skills you ant to use on her.
If you use steady/warding Breath on her, reducing her Speed will get her doubled more often, so she gets more special charges and activations.
Keeping speed only realy works if you improve it further, with Fury, +Speed Seal and mabye even summoner support.

Forblaze + special spiral is extremely strong with AoE specials, especially with heavy blade / infantry rush support and two infantry pulses, especially in chain modes.

As for Fae, both IVs are good; we had a question about this a day or two ago. +def -spd used to be ideal for the upper extremes of arena where bold fighter is rampant. I formerly recommended people just to stick with +spd anyways because you want your +10s to shine in PvE and +def -spd is significantly worse than +spd -HP in PvE, while you can just switch to +def on her breath in arena and guard. Nowadays due to bonus unit kill scoring, I think there's a new argument to be made for +spd -HP in the form of light breath windsweep, especially for Fae, who can use green infantry duel (by the way, it would make her very good at panic ploy, probably good enough to hit most 175BST armours). You can even stack some smoke on it, like, def smoke + atk smoke to support the Askr trio and Fjorm? 34 spd (+spd weapon refine; at +10 she reaches 38) will hit every armour in the game except +spd on some of the faster armours (Zelgius, for instance). You can also initiate safely on opponent Nowi and Fae because Fae has good res and you won't double so there's no ignis coming back at you unless they use water breath + breath skill + QR (and as far as I've seen they all use aether even though they're playing arena def).