I think the GH issue was resolved. The numbers agreed on are 6 dH or 110 ppm. This is soft water to an aquarist. The terms are subjective, but the numbers matter. I have a chart that so far as I have discovered is universally used within the hobby.
0 - 4 dGH 0 - 70 ppm very soft
4 - 8 dGH 70 - 140 ppm soft
8 - 12 dGH 140 - 210 ppm medium hard
12 - 18 dGH 210 - 320 ppm fairly hard
18 - 30 dGH 320 - 530 ppm hard
over 30 dGH over 530 ppm very hard
This is soft water.
As for numbers of fish, the tank dimensions are needed. As this is a 240 liter (63 US gallon) and 48 inches (120 cm) length, I am assuming the width is either 12 or 18 inches and the height, whatever. With this being the case you could have 100+ fish of the approximate size of rummynose tetras, assuming floating plants. My 70g was minimally larger in width/height perhaps, and I had over a hundred fish in there for years. May not remember all, but there were 60 wild-caught Corydoras, 21 Petitella sp., 12 Hyphessobrycon sweglesi, 12 Carnegiella strigata (Marble hatchetfish), some 8 Moenkhausia pittieri (Diamond Tetras, the last of a larger group acquired many years previous), 1 Rineloricaria parva that was then 9 years old, and one or two Farlowella vitatta. However, you are relatively new to this and I would not go overboard, but the point is that if you stay with fish of this approximate size you are going to have a lot of options. I happened to have my rummys in this tank, a group of 21, and they really should not be kept if this number cannot be acquired. I had two species, Petitella bleheri (the most common species) and Petitella georgiae which is much rarer. The photo below is the tank the day after I set it up, the fish (all except the Red Phantom that I acquired a few months later) went in later that day, they were in another tank, I had 8 tanks in my fish room.
We often get caught up (wrongly) on numbers of fish because we think solely of mass, but providing each species with adequate numbers, and ensuring they are truly compatible in all aspects (not only behaviour, but requiring the same environmental aspects such as decor, light, water flow, substrate) is what is matters to the fish, and they will be healthier with less impact on the system if they are truly compatible.
You want to have the plants obviously growing, especially the surface plants, and then you are home free. And you build up to the total stocking, just so long as the entire intended number of each species is added together at the same time, this is im[portant.