The RPO seems to be misunderstood a bit...yes technically the QB can eventually run, but that can happen on any pass play.
There are two types of RPOs pre and post snap. Pre snap RPO is basically an audible.
Presnap RPOs are generally based on defenders in the box.
Postsnap RPOs are just that, depending on movement of the defenders. Yes a QB can technically be called to run, but not on every designed RPO. A coach can absolutely dictate how often plays where a running QB is a possibility.
In a pistol two back option, the run of the RPO is done by the back with the read being done by the QB during the mesh point.
There are usually two tell reads, depending on the scheme: the TE on an end or/and an LB, usually the one over the 5, 7, or 9 hole, depending on the side, obviously. The read is on them.
The QB will pull and pass if the read determines it. Again, the read is pretty standard, but it’s also relative to the scheme and side of the field.
The read option is a pure derivative of the Wishbone, by way of the Flexbone, and birthed into the Pistol. In the Pistol, the QB is one of the backs who would carry the ball, and there usually is a jet sweep to mimic the spinning QB hand off right X/FB, turn pitch left motion to the Z or y back into the turn to QB keep Pitch option right from the wishbone. It is a power scheme.
There is a wrinkle where the QB, as he’s running with the ball in front of him and the lateral Y back, can read the TE break off a block for a quick pass either over or around the free DE.
So, though a QB can scramble in any play, there’s a difference between designed QB power runs, RO and RPO complemented by play action, or vice versa.