Yeah indeed he put a lot of effort into introducing the Dark Continent so I feel like it hints to how big and important this chapter will be to the manga overall, and I believe the artwork will only get better because I heard he's quite picky about the artwork, I remember reading that he insists on drawing all the chapters himself which is rumoured to be the reason his health worsened, it makes sense I guess, drawing manga is really taxing without assistants..
As to your question concerning his other work Yu Yu Hakusho, I wouldn't say I watched it, I only watched a few episodes and the beginning felt really dull to me unlike HxH and the bad animation really didn't help at all, moreover I heard that Togashi's health started worsening before Yu Yu Hakusho's manga ended and that he had to rush the ending, that kinda discouraged me because I'd like to maintain the perfect impression I have on this mangaka, don't want to watch nor read something rushed or ill-written, I hope you understand what I'm trying to say?