i m guessing they do since they have been close together for so long and also kno a good amount about tobi. if nagato does not kno of izanagi it might shift in his favor but who knos on that one.but tobi 1v1 is hard to beat i think there is a reason to why naruto got super-speed with Km he would be able to battle tobi easier if he has that.
I think he did bec Konan knew abt i t (well atleast the senju and Uchiha = So6P)
You must be registered for see links
Konan knew a lot abt Tobi and we can assume Nagato knew way more then her esp considering the possibility that he read from the tablet, he knows atleast that the sage used chibaku tensei of planetary size so he prop knows more abt the So6P then msot ave ninjas
You must be registered for see links
Not sure we can only use powers shown but maybe but that if he could he would be wasting a lot chakra using his own powers as well as controlling 6 paths and making them use techniques.
I don't think they would waste a lot of chakra to the point of collaption
but if it were true then I would use the 6 bodies has taijutsu weapons to overwhelm my enemies while I use the 6 path abilites and other long range jutsu to reign hell, the possibilities are endless man