So get this. Luffy can hang out with his giant pals now, they're his equals. If Joyboy was already a giant with the same powers, who did he hang out with ?
Super interesting for me is Brogy calling Nka "this" god and laughing about it, like it's not really serious. Might be there are other gods (Elbaf and so on) and they were all real. Makes Nika seem less important than previous chapters implied. He's not THE god, he's just a cool god. Funny guy, nice with his friends, but not necessarily our saviour.
Cool thing too is the gorosei are not surprised at all about Luffy's powers. They've seen this shit already, maybe on a greater scale. Luffy claps Saturn into a pizza, he counter attacks immediately. Warcury's blast tries to erase Luffy's existence. They know they live in a cartoon, like Luffy will learn soon. I guess they're gods too. Or maybe that's what awakening is : )
Maybe that's all conqueror's haki is : you know your reality is malleable, so you influence it. Nika might only be the ultimate Conqueror. Maybe the gorosei really don't have devil fruits. Maybe this is all just what really strong and ancient conqueror's haki does. Saturn shapes his into spider legs and stabs you with it. Or he condenses it into bullets that he spits at you. The gorosei look out of traditional paintings, Mars especially. Maybe Imu painted them with his brush and gave them part of his haki, like satellites. D is for drawing.
Bonus theory : what if it's all linked to the crazy sizes and ages in one piece. Joyboy and his friends weren't giants, they were just humans. But their foe (a mix of imu and foxy in my mind lol) hit them all with something to reduce their sizes. Centuries later, some huge people remain, but average size is going down. Luffy isn't a tall guy, and next Joyboy could be even smaller and his task even harder.