Summer frederick ivs

I got 2 good ivs for summer frederick one is +atk -def (this doesn't hurt that much as he really shouldn't be tanking anything) another is +spd -hp (got this one for the legendary banner i think)

i'm not sure which one i should invest on... I plan to make him a debuffer who can hit hard. I also want to give him windsweep and phantom speed.

Which do you think is best? I think +atk is a good one since i could just give him darting blow and with spd buff 41spd when initiating and he could still pack a punch. Another thing. Should i give him smoke or rouge dagger? Or should i keep the seashell for additional stats on his first atk.