We do have on-screen example in the early seasons of Voyager being at Warp 2 with it's nacelles down.
Granted, it might be explained as an VFX error of course ... but it also fits into the theory that the ship can achieve low warp velocities without raising it's nacelles.
If SF was ordering it's ships to avoid tear of subspace by limiting themselves to Warp 5 ... it's entirely possible that the Intrepid class was actually meant as a prototype class that SF would learn from in order for their ships to be able to sustain high warp velocities without doing damage to subspace (which hopefully was settled by the time of post TNG).
I would imagine there wouldn't be that many Intrepid class ships in service as a result ... then again, there might be and they would still retain the folding nacelles option as it also might have allowed SF to upgrade the maximum warp velocity of the Intrepid.
We know that the Prometheus ended up being the fastest in the fleet, but by the time it rolled out, I would have imagined SF upgraded the velocity of their Intrepids even further.
Older ships would likely still be limited to a specific range, so it's possible the folding aspect gives the Intrepid the advantage of pushing it's engines even further.