I've lived on a few coasts: NY, especially Long Island; Georgia; Texas; Southern California; and Florida.
By far, Florida was the most corrosive environment.
I never needed to do anything special with my bikes in SoCal or NY. But on the Florida Gulf Coast the combination of relentless humidity and salt air made even my stainless steel and aluminum fishing gear rust and oxidation incredibly quickly, even when I rinsed them in fresh water after every use. Everything I saw in that area showed evidence of rot from humidity and salinity. I didn't have a bike there but I'd expect it to need as much routine cleaning and maintenance as cars and fishing gear.
Regarding the simplest spray-on type lube/protectant, the best I tried in the 1990s was Birchwood-Casey Sheath. It was mostly sold for the firearms market but works on any metal. The name has been changed to something else but it's still the same stuff. It's a polarized protectant, so it spreads to all contiguous metal surfaces to reach beyond where it's sprayed externally. I tested it against several other similar products (including old fashioned RIG -- rust inhibiting grease -- similar to cosmoline), various lubes containing PTFE/Teflon, etc. Sheath consistently outperformed those in outdoor tests on a covered patio and in a shower on identical pieces of blued carbon steel.
There might be a few delicate items that wouldn't be suitable for that spray, but I can't think of anything on a bike that would be harmed by it.