You can take a train and Nasik Road is the station , from there you can book private cabs like Ola Uber. It will take almost 45 min ( depends on traffic ) for the 25kms.
Train, Bus and Car all are fine. We went there on our TVS Wego (2 wheeler). Road is nice and it is around 3-4 hours drive depending on which part of Mumbai you stay. Do cover Sadhan Misal and Famous Kulfi as well. Sharing our experience. You can check the link for more info. https://www.youtube.com/watch?v=zK82dpxkw08
Mumbai to Nasik travel could be planned either ways- by road or by rail. Trains I normally prefer when there is pre-booking done. Stations are crowded always and we don't have cushion for the time lost in getting the ticket from the counter. However, cabs i.e shared cabs are also a good option. Moreover, if SULA is also on the cards better to choose a cab so that you don't hop on and off frequently. SULA has "BEYOND by SULA" where you can book your stay. You can use undermentioned link to book your stay here-
https://www.agoda.com/partners/partnersearch.aspx?pcs=1&cid=1884392&hl=en&hid=6687254 Highly recommended, if you want to enjoy SULA.