Congratulation on getting 2 L!Hector (and even two with this sweet atk superboon! and one perfect iv)
If you merges your -res into the -spd one, you’ll get +3spd (kinda useless at low merges) +1atk and +1hp.
Personally, I would advise you to not merges him instantly (even if for me it would be worth it) because -spd is his best bane and doesn’t have a lot impact at low merges. (So i’ll take the +atk -spd and keep the other)
L!Hector can be builded in a lot of differents ways, and even more with +atk.
You could stick with his kit DC+ VF, slap aether on him, DD3/ def/res bond on S slot and you’re done. He’ll be insanely great with it because of his weapon that deny double and is very easy to activate, it turn him into a defensive powerhouse (outside of infantry with null follow-up) because only taking one hit up his bulkyness by A LOT, he could even be considered as a mixed tank with only 26 base res thanks to his prf effect.
You could also swap VF by SF for cd deny + acceleration and slap QR S slot (a classic build too)
You could also use a classic Brave axe + bold fighter, that also work wonderfull with his huge 44 base atk.
The only skill kinda hard to come by is BF. Aether for the sustain every two fight (or on the 3rd hit but it won’t regen much, because two hit at 62atk is often making the ennemy getting low on health.) Ignis for a 30dmg bomb every 3rd attack. Galeforce is also possible but you’ll need quickened pulse S slot for the situation where Hector will kill his first ennemy in only 2 hits.
You could also swap his prf for HoL but I wouldn’t advise for this because his prf is already REALLY strong (one of the strongest actually) defensively, his only weakness is null follow-up (but a lot of armored got messed hard by null follow-up)
If you want another cool build that work really nice, it’s this one :
It’s more for AR offense as galeforce armored team vs almost full ranged unit: The crux is to engage one, kill him, galeforce on another (and kill him), the other galeforcer who got DC/dc weapon (very important) kill two ther unit, and with DD4+DD3 Hector will be virtually indestructible for the 2 last units that’ll attack him and not the other galeforcer because Hector won’t hit back (and so the IA will count this attack as a “win” because they’ll deal more than 5dmg they suffered, that’s why they’ll hit Hector and not your other galeforcer) contrary to the other galeforcer that’ll hit back thanks to having dc/dc weapon
(this hector at +0/0 survive a +atk +10 LnD ophelia if he got +6res buff and kill her at your phase)
PS : unit builder because i don’t have a L!Hector at +0