The "correct" way of doing things in vaping is whatever works for you. Everyone is different so what works well for one person won't work so well for another.
If the 25 mg works for you, stay with it for awhile until you're totally off the cigarettes. Once you feel comfortable, go down a little - I would suggest down to 21 or 18. If you go down too fast you'll either wind up back on cigarettes or you'll just wind up vaping more often to get the nic your body craves.
Your question takes me back some years... anyway, we used to tell people that if you smoked lights, 12 mg would be a good starting place (not salt nic, the regular nic). If you were smoking regular cigarettes like Marlboro reds, then a 24 mg would be a better starting place as that would be a closer equivalent. Does that help?