Gowther's attacks the mind, but he attacks the mind with his Magic. So, a stronger Magic stat strengthens his ability to attack minds. Spirit seems to give a better resistance to some of his mind attacks. He said himself that his AoE Blackout would effect people with a Spirit stat of 400 or less.
There is no evidence that Full Counter is stronger when he has Lostvayne, maybe it's not. But Full Counter doesn't have power in the first place, it's a reflection ability. Anyway, it's been made clear that he is stronger with it and the special ability helps a lot. Con
Escanor used Rhitta to defeat Estarossa and Meliodas, but he didn't use it for his final attack. Rhitta doesn't suppress his power, it stores the heat coming from his body. When he saw Meliodas transforming, Escanor who was without it invoked it immediately for a reason. When Escanor is wielding his weapon he doesn't become weaker or anything. Escanor didn't imbue Rhitta with Sunshine for reason even though he could have done it. I think you are paying too much attention to what they said about ST "drawing out" more power. Basically, what it means is that fighters are much better with one, and it's evident in battle. It's not like they can't use powerful attacks without them. King's Release is an ability and it still confuses me for the same reason as you. To make things clearer I asked FKS a long time ago
here. His reply is just below my post. Meliodas used a different word but King's Release definitely counts as Chastiefol's ability since he used the same word as Escanor for his Charge & Fire. The origin of the STs will be the key to solve all of this, but what we know is that:
- They got them from Bartra.
- They allow them to use their powers at the fullest.
- They have a special ability.
It's worth mentioning that we have never seen Winged King actually uses the word Release on a page. Nothing says that he can't use it with True Chastiefol like that.
Why not? They say many times how important STs are even after this saga and the Sins are better fighters with them. Three Sins were involved in the Great War. Meliodas had a big sword, Gowther had apparently nothing and we don't know what Merlin had but Lostvayne and Herritt do help these two. There is no reason it would not help the others. Moreover, even if the weapon is not ST tier, a weapon makes them stronger. Ban uses whips or three-section-staves for that reason. He had one in Bandit Ban, and he makes it clear here:
As I said above we need more explanations but we do know that Sacred Treasures are weapons of the highest quality. Even someone like Meliodas didn't have one until he met Bartra Same for Gowther and Merlin. Bartra definitely knows a lot about them since he gave weapons of that quality to lower ranking HKs. Commandments who use weapons are Zeldris, Estarossa and Galan but we don't know how good they are(worth mentioning that Galan praised Rhitta).
If the Giant Diane is better when she uses Gideon for Creation(which is shared by all Giants besides Dolor for some reason) there is no reason Matrona or the others would not be better with it. But you have to get a weapon that good in the first place.