I know tobi is an alias used by both obito and Madara. The tobi that visited itachi was Madara. You can tell by the way his hair is way different from obito's hair has ever been. Also, I believe the tobi that control the mizukage was madara. I can't believe that tobi was obito under any circumstance. Anyway I believe that after Madara died obito took on the name of tobi, probably after madara train him for awhile n we have The story thus far.
Well the Tobi that attacked the 4th had long hair
and a different mask like your description. But
the thing is, Madara doesn't use Kamui nor
does he fight like "Obito". Completely
different fighting styles.
I think,the men who controlled the 4th Mizukage
and ask Kisame to join him is not using the mask
though...you can see how surprisingly Kisame when
Tobi open his mask...then,I'm sure,they are
both a different persons...
he have a long hair
when he attacked the 4th Hokage?...I don't
see his hair is long...and,his mask is definitely
same as the mask that been used by the one who met
If the 4th Mizukage is what
you refer to,the men that controlled the 4th
mizukage has a long hair,but it never been showed
that he weared a mask...that men long hair looks
very similar to the one who met Itachi...