Stronger flavours are better in winter if the bite is slow. Start of plain and experiment as you go.
Bloekom, garlic, onion and duiwelsdrek. These are strong so use a small amount. I hardly ever use flavours, sometimes in winter and then just a drop on the bol and nothing on the tiger.
I use plain bom with molasses mixed in and plain or sweetcorn tigernuts and it has always produced.
Where you place your baits are more important than distance. Often the middle of the river is not the deepest. Rather find drop-offs with gravel or mud bed and place your baits there.