The higher the number, the better the drape on beading wire. For example, Beadalon 7 would be stiffer than 49 strand.
Depending on the size of the beads (and their weight), you would use a heavier weight (thicker diameter). For example, .024 is heavier than .013. Because these beading wires are nylon coated, they don't tend to get cut through by beads or crimps, but if they are kinked when worn or stored, the stainless steel core can break.
Remember that, of all jewelry, bracelets get about the most rough wear! Silk might just not be sturdy enough.