Hmm I don't think it's useful to compare the sins STs to how the demons fight. Just look at the red/gray demons. They don't have weapons either. The STs were designed to draw the full potential of the sins. Not gonna dwell on that too much, but a sin without his ST, wouldn't be able to access his power entirely.Doesn't mean he's entirely useless bare handed, just look at Ban before he got that staff. Then there is the fact that Mel didn't use his ST till recently. I don't think the difference is that huge between a normal sword and his ST, because he uses Full counter mostly. So I really don't see why the demons should fight like the sins and all of them use weapons, let alone weapons that could allow them to access all of their power. Like you said, they hardly need that with a PL of 30-40k. It's just too high and seeing how the sins are getting their asses handed to them by one demon with 26000 for a power level, I think the demons are pretty competent even without their weapons.I can see some of the demons have kinetic powers,like the two girls and the mask cloud, so it would be really useful for them to regain their magic. Galan fights like a dragoon to me, he is extremely flexible, quick and his strength is remarkable. His weapon which looks like a mix between a scythe and a halberd was particurily useful against Mel's clones, and like you said it fits his fighting style.That is pretty much what I meant when I said it could be a matter of preference. For example, zeldris has a sword but he does not need it to be able to draw his power out, he simply is a swordsman. Still though, why the difference? We have seen meliodas, diane and ban fight without a weapon and due to that we know that what they can do without weapon is worthless for the most part. Without weapons they can barely stand up to an above average knight. I mean, we saw 3 of them against guila and they couldn't land a hit. Meliodas does not like killing people but even then him, let alone diane and ban, had never hesitated to beat holy knights half to death for daring to stand up to them. Ban killed the holy knight who captured him basically for the lolz considering there are absolutely no grounds under which a revenge on ban's part is even remotely justified even if the holy knight in question was evil. Ban allowed himself to be captured and tortured after all.
There are at least quite a few commandments who don't seem to carry weapons. Estarrosa, the 3 girls, the guy with multiple arms, the black mass with the masks... Of course, power levels which I would guess would be between 30 and 50 k could defeat a ST armed sin easily even if they needed decent weapons to draw out their power. The first holy knights we saw probably had power in between the 300 and 800 range and the sins easily won... Right now the situation seem to be that the sins have at most 10% of the total raw power of the commandments. And the idea that they could use the extent of their power without the need of weapons is terrifying. Even when meliodas was transforming against helbram it kinda seemed like he was in need of a weapon. To me it kinda looked like he displayed more power with liz's sword during the kngdom invasion arc...
I am not sure if fairies need weapons or not at this point. King is in a murky area considering his weapon is a piece of the sacred tree. Helbram used a sword along with the sacred tree. 200 years ago when king originally killed helbram he did not have a weapon. And at the time he had already been the deterrent to war against entire kingdoms. recently we saw some fairies using twigs and stuff against the albion too.
I think having more variety wouldn't hurt. If all the clans and races fought the same way with magically enhanced weapons the manga would become redundant, and it would kinda take away the impact of the demons having huge power levels, despite having their power depleted.
The fairies seem to use branches and parts of the sacred tree primarily, so yeah I don't think it's necessary for them to use weapons like humans.



