What if Aragorn had chosen differently at Parth Galen ?

[The Mouth of Sauron]

After the departure of Boromir, Aragorn had to choose whether to try and find Frodo and Sam on the east side of the Emyn Muil, or whether to follow the Orcs who had captured Merry and Pippin. As we know, he led Legolas and Gimli to follow the Orcs into Rohan.

But what would have happened if Aragorn, Legolas and Gimli had followed Frodo and Sam instead ?

- would they have found Frodo and Sam in the Emyn Muil ?
- would Gollum have played the part he subsequently did ?
- would the victory at Helm's Deep still have happened ?
- assuming the Ents still destroyed Isengard, would the Orthanc palantir have come into play ?
- presumably the Dead would not have been summoned and South Gondor would have been lost ?
- etc., etc., etc, ?