Assuming Bell didn't create Y&R and took over as HW of AMC after Agnes I would assume he would have kept the show fairly similar to her vision. While giving it more of a psychological slant, a little darker, less humour. I think there would have been more singing and more crazies running around Pine Valley. I think he would have played up the Brooke/Erica feud more and Erica would have become Jill and Mona would be Liz, I say that only because they already fit that mould anyway. Stories would have moved a lot slower. He would have had a writing protege like Pat Falken-Smith or Kay Alden who would have taken over after he retired.
When I see B&B I can see similarities to Y&R but Days didn't look like Y&R at all, which says to me Bell was capable of taking someone else's vision and adding to it, rather than gutting it and making it what he wanted. Established characters didn't suddenly change personality just because Bell took over, and the ones he added don't come across as early versions of the ones he created on Y&R or B&B.
As for Agnes if she hadn't created any shows and simply took over Y&R at some point, I think we would have seen a lighter show, even more family oriented with heavier social issues. I think it would have moved a lot faster too. It is harder for me to comment on Agnes as I haven't watched a lot of her AMC and OLTL.