& welcome to the forums!
Sounds like you have a good plan there so far, as long as you add the fish slowly over time a tank that size and with an adequate filter could easily house a school or 2 of different danios/tetras, I would go with 10-15 of each type that you want.
You could also have either the haras or kuhlis, both are really cool fish.
With gourami you will want to stick with the dwarf variety as the larger ones will eventually need a bigger tank, if you pick dwarf try to get a male/female pair as two males often fight when kept in a smallish sized tank. Honey gourami in my experience are a bit more peaceful and you could probably have a couple males with no issues.
All these fish are compatible in my opinion especially in a planted tank and seems like a well thought out stocklist.
You can plant the tank any time, personally I would plant it on day one so as it cycles the plants will be established by the time you begin adding fish, they will also help with the cycling period as they use up excess nutrients and gives the beneficial bacteria more surface area to colonize.
For a filter I would go with a decent canister like an eheim or fluval though some people do recommend the cheaper ones, I have found you generally get what you pay for in this hobby though. An eheim 2215 or similar or a fluval 304 would be my first choices.
Hope I have answered a couple of your questions, we love pictures around here so feel free to keep us updated with the progress on your tank!
