As for RZA, his flow never really bothered me that much. It's more his voice that I find grating, and his poor enunciation (I understand that's not really his fault, but still). He's actually quite capable of slaughtering a track in time, and experimenting with unique, interesting flows, using internal rhyme schemes, multis, and so on. Check his flow on Assassination Day. His use of monotone and big vocabulary may not be for everyone, but I think it's a unique style (and a ton of indie rappers copied him for it back in the late 90s / early 2000s).
I was always a fan of Silk's delivery. He was one of my favorites in No Limit growing up. All my friends clowned me for it. I don't know what it is. I don't get why he's so hated for his flow, and no one seems to get why I like him.
I suppose I can see how sometimes it seems like he mistimes the beat, like when he speeds up his delivery within a verse and rhymes off the beat, but I always liked something about his unconventional, explosive energy on these tracks. It felt deliberate and distinctive. I also like his voice and his laid back conversational style on more downtempo tracks like If I Don't Gotta. I can't fully explain it. His early stuff is just dope to me.
As I've said before, Vlad is old and out of touch. He's pushing arguments that meant something back in '99. But now at 20+ years deep in the game, Nas more than has a body of work that speaks for itself. Can't think of any artist that has as many great albums as him. It's pretty unbelievable if you think about it.