Dakki should be added to your hand to Normal Summon her when starting your synchro climb. Although if you have Shafu you can pitch Dakki and revive her with Shafu’s effect. Yuki-Musume does not really care whether you add her to hand or pitch her to the graveyard because her effect can be used from both places.
The decision whether to add to hand or pitch Mayakashi Winters depends on whether you want to use its debuff effect or revive effect respectively. Generally you want to add it to hand to make use of more of its effects, and use the revival effect as a backup.