I keep my Rio240 normally about an inch below the max water line without issues, but then I've seen local fish stores and read about having the bigger gap above the water. I think I've read that in the wild (where there are two different groups that have different DNA going back ~65 million years ago), these fish will actively jump out of the water to try and catch flying insects.
Lighting is something that currently concerns me, as my Rio240 came with the T5HO 108W setup, which I want to change for a dimmer T8 setup with those purply "tropical" type tubes. The tank receives some mid-afternoon direct sunlight (when "sunny" Southampton weather permits), so I only turn on the lights for a maximum of 6 hours a day, to keep the Echinodorus ("rose"?) plants happy, which the ABFs tolerate without showing signs of stress (in the evening I make sure the room's light is on when the T5s are switched off for a more gradual darkening). Something you could do is use suction cups to secure a few small pieces of bogwood around the water level having tied a small Anubias variety (eg. barteri nana) to each piece (these plants grow at the water's edge in Africa, but they tolerate being submerged in aquariums) to provide shady spots.
Your tank is larger than my Rio240, so yes, you could combine ABFs and GWPs. Both species can be kept as singles, but they both also have a semi-social nature and yet males of both species are spiteful to competition.
In addition, like I wrote yesterday, male GWPs often harrass the females, so hareem setups help to give each female a stress break (as does lots of upper water line-of-sight breakers with plants and/or furniture so the females can hide). I started with three females and a male last summer and sadly woke up one morning to find a dead female, but I have no idea what happened, as at that point my male was being relatively well behaved (unlike recently where he was nipping females). A couple of months later, having emptied the tank for my aggressive Lionhead Cichlid parents, I was amazed to discover three ~1cm babies over the course of a couple of days. They were hiding in the Red Root Floater jungle, but I moved them into a breeding net, where a single beautiful boy survived (they were quite nasty with each other, perhaps three boys) to ~4cm and I then rehomed him to somebody local.
