I have a Roma 240l tank. I bought it many years ago with T8 lights. I have recently retrofitted LED lights, but made an error when trying to work out what length lights I needed and got lights that are a size too small. This means that I will have less light in my tank than you!
I also have soft water (but not as soft as yours) and found that a lot of the stem plants that are sold as starter plants need more calcium than soft water can provide. The plant supplier's websites are really good for identifying the ideal water conditions for plants. I've always used the Tropica website, but
@Matt recently pinned a brochure on one of the boards here, and that is also excellent and has some different plant selections.
The list of plants that I currently have (and therefore know that they are suitable for a low tech tank) are:
Various types of crypt (planted in the substrate)
Two types of java fern (on wood)
Bolbitus
Vallis (I can't spell the full name!) (Planted)
Anubias (on wood, rocks and also just rested on the substrate, where it happily rooted)
Nymphaea Lotus bulb (planted)
And a slower growing stem plant, whose name I can't remember (planted)
In a previous life, my tank was moderately high tech. I supplemented the T8 lights with various leds, added CO2 gas with a compressed air system and had a fairly heavy fertiliser dosing regime. Since having children, I have switched out the more demanding of the plants I had and am part way through re-establishing as low a maintenance tank as my chemistry understanding will allow me.
I have a substrate made up of Eco complete and gravel and an area of sand. I have recently sieved all the eco complete and gravel mix so that it is less than 2mm diameter (I didn't want to replace all my substrate with sand, so just saved the smaller stuff).
There is a lot of inspiration on this site as well as helpful advice.
Good luck.