I don't have any personal experience with gourami, because I researched and thought like hell about them for a while, they just weren't my cup of tea. I don't remember hearing anything about 1:1 being a bad female/male ratio, like other fish who need more of a 3:1 ratio (like any livebearers you might plan to have in your tank). I saw your video and I don't think I saw any real plants. I was wondering if you ever thought of adding any live plants? The only reason I make mention and encourage this is because the fish you plan on keeping in there would look stunning against plants, and I believe fish like those tetras would love the addition of plants. Also, a small technical thing might be considering changing the gravel. I've had neons, rummy nose, black neons, and they've all looked so brilliant against my black fluorite gravel. The colorful gravel you have might compete and downplay the brilliance of your fish like the cardinals.
I would definitely advise against getting neons as they are definitely NOT hardy. If you look on this forum there are several threads about how neons have been inbred thus weakening those that have been tank-raised (which I believe are the majority). Cardinals are much hardier AND as my friend always says, that solid red band makes all the difference. I definitely side with Lupin when he says to get Cardinals.
Also, with the advice about ottos vs. bn pleco. I think that is up to your preference and bioload. My ottos are small, active as hell, and 3-5 should do the job for a 20 gallon planted tank (if you decide to go this route). I have no experience with bn pleco, but they don't look the coolest, to be honest (just my humble opinion!). I do think that bn is a really cool alternative to ottos because they probably won't outgrow your tank. many being from 4-4.5 inches.
What kind of filter do you have? Unless I looked over this piece of information...