Hi guys I have been thinking about Doflamnigo's DF and I have come up with an explanation. I think that doflamingo has the puppet-puppet fruit parmecia type and he uses it in conjunction with haoshoku haki and busoushoku haki. I will explain how in 2 points.
1: Haoshoku haki
I think Doflamingo got so advanced with haoshoku haki that he can use it in conjunction with his strings. example, he makes a hand gesture and it takes control of the person. The only way to get out of it is if you use kenbounshoku haki to see the invisible strings before they touch you and get out of the way. Another way to escape it if someone could break the strings you are being controlled with for you.
I think Doflamingo can use busoushoku haki so good that he can make his strings strong and invisible because busoushoku haki did say it can make invisible armor so why not on strings. Doflamingo can make the strings deadly by making them denser with bousoushoku haki .Thats why he was able to cut off Oars Jr.'s leg.
If this theory I predict is true, then Doflamingo is deadly.
Also I don't no about that Sky Path thing but you can give your idea's about it in the comment section