salt water fish are osmoregulators and have to balance their osmotic pressures differently than inverts, which are osmoconformers. An osmoregulator is much less sensitive to differences in salinity, as long as the difference is not that significant. If you know that the source water that the fish in the bag has not been treated with copper, I say to float the bag.
With inverts and cnidarians, I typically do a float and pierce the bag with a knife once every fifteen minutes to half an hour and let it acclimate. Drip is good as well, but I also put a small heater in the bucket that is acclimating.
When I owned my store, I had set up a saltwater acclimation station, which consisted of a row of three 10g tanks and two 5g tanks in the back. My main pump was connected to the acclimation tanks. When I would get a large order, I would put all of the water and everything from multiple bags in the same tank that could possibly go together, with a small heater and an airline to pump air into it. I'd hit it with a little prime or amquel and then start a two to three hour drip acclimation. I rarely lost fish that way. I had separate tanks for the inverts and corals - which was easy to just empty and go. But, then again, that's a commercial business way of doing things compared to at home stuff.