There is rarely any choice in this. Most C41 and RA-4 kits only come with combined bleach/fix, so I think we can assume that it works just fine.
Having said that, the C41 kit I would recommend has separate bleach and fix:
https://ntphotoworks.com/product/bellini-c41-kit-1lt/
I've used several of these Bellini kits with great results. The mixed chemicals keep for weeks without any special precautions, and colours are always bright and clear.
For paper, the small Tetenal RA-4 kits work well, although Kodak Ektacolor chemicals work out much cheaper in the long run