Split lids are the go, I built my own boat fridge for just that reason--couldn't see a durable plastic cased fridge on the market with a good split lid arrangement.
I use a fish bag a lot. I live on the edge of the tropics, and regularly go right into them, hotter than you where we are, not so humid as FNQ. Name a type of fish storage, I've tried them all. Both amateur and commercial. You can shove your moulded plastic ones are far as I am concerned, none of them hack it here in real heat, you simply can't beat laid up GRP with 3 inches of foam. If you only want to day trip, the better quality fish bags are fine. There are cheap rubbish ones out there, just avoid them. I have used a couple of different sizes of the Madfish, settled on the medium, 140 cm inside. I've never seen a Madfish punctured by spines, you can even keep crayfish in them. I'd be confident on overnighting as long as you started full.
I'm all about getting the deck clutter off, as well. I had a divided compartment with two lids as standard on the Reefrnner. The divider was easy to get out, then you have a large fully moulded compartment underneath. I was initially getting the bag in through one hatch, then I had a shipwright make it into one big hatch.