I feel like voice acting and the music is what makes vns different from the rest. It even makes me a bit angry when a vn has no title menu song. As for voice acting, it is highly preferred but I would still consider reading it if it doesn’t have it. I find myself waiting for the voices unless it is a really exciting part that I must know what happens next… It doesn’t really slow me down because I am not afraid to cut them off when I want to…
For me, I like when they use the full potential of vns, have good music good sound voice acting, choices, and maybe even a mini game or two. Doing all those things that can’t be done in books add an extra layer of fun for me. But at the same time none of those are required just enhancements…
Well my rule is if it isn’t causing you to have more fun and enjoyment turn them off. But I think for most people voices adds a extra layer of enjoyment and fun.