Which azwan mode is capable of the highest leveling exp for the 40-120 range?

Not honor, just for grinding through. Soloing and Partying, if it changes which mode is the best for it.

If it matters, its for my brawler~

and also, does the Aswan nerf affect both character exp AND Honor Exp? or just one of them?

Do you mean the aswan nerf of the removed world war thing or the aswan nerf that's in the current kmst patch?

If you mean the world war one, it's just the removal of how useful aswan is all together. The map layouts for hellmode and such are changed. I can't really remember but I believe honor exp is gained differently also after the patch. Basically the patch just makes aswan useless and a ghost town.

If you meant the current kmst patch with aswan returning, exp gets nerfed 50% from most mobs.

Regarding your first question, hell mode is the best with a party of 6 in 3rd job. 40-70 aswan isn't much use to you.