I have a male/female pair of Banded Gourami, and they are really nice looking and compatible community fish. My male is fully grown and stunning blue and orange colours.
However, unlike most Gourami, they do spend a lot of their time in the lower part of the water, so this is where your hiding places need to be. They can also be VERY timid, and can often hide when you approach the tank - especially when just introduced. It will take them a few weeks to be properly settled in. Like all fish, how timid/brave they are will depend upon the individual personality of the fish, but over the last few years I've kept two different males and a female, and they are all timid and spend alot of the time near the tank bottom. When swimming out and about in the tank, they will visit all levels of the tank though. You can use a shoal of 'dither' fish (e.g. Tetras or Cherry barbs, etc) to make them feel more confident, but be careful not to keep them with anything very active or aggresive. The Banded Gourami is big enough to be kept with other large(ish) fish (4-6 inches), but in your 20 gallon I'm assuming that won't be the case.
My 35 gallon tank is set up specifically for gourami - lots of plants, dark substrate, floating plants, wood and rock hiding places.
I would try and set up your tank to be fairly heavily planted (whether real or plastic plants), this will give them areas to hide in, and make them feel confident. A dark gravel/sand will show up the colours of the fish (especially the male) better.
As with all Gourami, floating plants are highly recommended to give them a secure feeling. Or you could use some some large overhanging plants such as vallis to cover the water surface. Once settled, the male may even blow his bubble nest amongst these. Try to cover a good portion of the water surface.
Mine have a cave to hide in that I constructed out of pieces of sandstone - obviously you could use pieces of bogwood, plastic ornaments or caves etc, but I would recommend somewhere for them to hide. Basically, they feel much less stressed if they have somewhere to run and hide if necessary.
Gourami also do not like fast flowing water, so try and keep the water well filtered but still. I do this by using a spraybar on the outlet of my external filter, directed against the glass so there is no fast flow of water across the tank.
I keep all my Gourami with shrimp - Cherry, Ghost and Amano shrimp, and none of them bother the shrimp at all. If the shrimp are very young or very small (i.e. they might fit in the Gourami's mouth), there may be a danger they would get eaten - but that's the same with all fish. Having plants in your tank is also important to give the shrimp places to hide. The Banded Gourami will feed on flake as a basic food, but I give mine frozen foods (bloodworm, daphnia etc) most days too. It's much more natural for them, and they will colour up better too.
Phew, that's alot of writing. I hope some of it was helpful!