Things get a bit conflated in SC. To break it down, consider 3 layers (within the game universe)
Every point in space has a Supercruise maximum speed. This is the total overall maximum reduced by the gravitational field strength* at that point.
Most of what is experienced as acceleration and deceleration is actually the effects of the local maximum changing as you move through space.
On top of the space layer there’s then the hardware layer. This sets your thrust in relation to the space layer. This is where your actual acceleration and deceleration is set, but in most circumstances you will not be able to tell, because your movement through the space will have a much more dominant effect on your speed and will be what results in your experience of acceleration and deceleration.
On top of the hardware layer, there is also a software layer. The software layer adjusts supercruise to simulate a Gravity well for targets which don’t have them. This makes it more practical to supercruise to, and drop out at, targets of that kind.
Acceleration and decceleration rates are actually incredibly high. Away from gravity wells, your ship will do 0-600c in a second or so.
Anyway, this helps partly answer your question OP. What mostly gets called acceleration and decelleration is the same for all ships because it’s part of the space layer. It’s nothing to do with the specific ship. It’s a result of movement through space.
Does the actual acceleration differ? I don’t know. I’m not sure if anyone’s actually tested it in a way which would actually determine it. Turning in real space is a result of acceleration, and turns in SC vary by ship, so quite possibly the straight line acceleration also varies by ship in SC. Equally it’s quite possible the turn rate sense of acceleration and straight line acceleration were decoupled for SC.
I think that pretty much covers everything raised in the thread.
*For info SC uses a Newtonian style gravity model but the fall of is at a higher power of r than the r^2 from Newtonian gravity.
