You are correct, you can have problems with Future—or any acrylic—in conditions of very high humidity, because it is an aqueous solvent system. With very high humidity, solvent (water) loss to the air is very slow, but polymerization proceeds at its normal pace. This can result in solvent (water) being trapped in the coating, producing a hazy effect, and causing the surface, or even the entire thickness of the coating to remain soft. Once this happens, fixing it is problematic.
The solution is: apply the coating in very light, thin coats, insuring that each is tack-free before recoating, and use an acrylic retarder. This will slow curing, allowing extra time for the solvent to escape. Allow plenty of time for this. The ideal recoat time is just after the first coat is tack free. Also, if you are overcoating acrylic paint, be very sure that it is completely cured before applying the Future.
The effect on a gloss lacquer may be less, but this depends greatly on the resin used to make the lacquer. Some of them are hydrophilic, and will trap moisture in the coating, especially when applied as an areosol.