Snake will stick C4 to a fighter on frame 9. When you d-throw at 160% you have +6 frames advantage, which is enough time to u-tilt (comes out frame 6) but not enough time to sticky.
For reference, d-throw has -4 frames advantage at 0%, and +3 frame advantage at 100%. It climbs to +4 around 125%, and so on, so you can tech chase with this throw a lot better the more percent the opponent has.
(^ Correct me if I'm wrong here, going off by memory)
With that in mind: sticky out of d-throw may work better at around 100% if, say for example, you predict where the opponent rolls. At 160 just u-tilt, it KOs everybody and is guaranteed.
I have not been able to stick people when I down throw them. My understanding was that you could not. Side question, can you stick people that are shielding?
Yes, you can sticky a shielding opponent. This is a very good way to punish shield, especially if they are above you in a platform shielding. Works well in this game because dropping shield is much slower than it was in S4 (it is 11 frames of shield drop in this game). Because this isn't a physical attack, sticky can't be parried as well.