I had never bothered to make this calculation, but always sort of assumed that the Sun would look like a disc from those distances... very small but still with a disc shape easily discernible by naked eye. This made me do the calculation. Turns out that the Sun looks almost exactly the same size from Pluto (at perihelion) as Venus does from Earth (at their closest distance)! However, venus at its closest is bright enough to cast discernible shadows and Sun's absolute brightness is a LOTTTT more than venus.
So, yes, you are right. just another star in the sky that is however *much* brighter than anything else. For religions starting on pluto, you can easily bet against anything other than the Sun or Charon being their chief deity.