Aquariums: My first try at Iwagumi

As the title says, this is my first try at an Iwagumi-style tank.
The tank is 120cm (47.24") W x 50cm (19.69") H x 40cm (15.75") D, so it's going to be close to 200L or 52.83 gallons.
On the bottom, I used filtration wadding to protect the glass bottom from point loads from the lava pebbles and bigger stones. Talking about the pebbles and stones, I used lava pebbles to create the elevation difference in the tank as they shouldn't start shifting over time. I used sand as mortar so the lava pebbles are even more sturdy.
The big stones are somewhat of a problem, though. They should all be Seiryu stones, but the shark fin-shaped stone has some white veins in it, which makes me think it's a Ryuoh stone. I didn't notice it when selecting them out of the bin; they were pretty dusty. But after scrubbing and boiling them, I noticed the veins. I probably would have bought it anyway. I really like the shape. I know these rocks are going to influence the KH values, so I'm planning on getting a reverse osmosis system because I want to keep Cardinal Tetras in the tank.
On top of the lava pebbles, I'm going to put a layer of substrate that's easy for shaping. On top of that, I'll add ADA Aqua Soil. I'm new to Aqua Soil, even though I've had tanks for about 30 years now.
For plants, I'm going to use some Parvula (Dwarf hair grass) around the stones and to cover the rest, probably HC Cuba.

I've watched some videos on how to go about setting up an Iwagumi style tank, and I came across someone who did a "dry start." I'm probably going to give this a try, as it seems to be the best and most convenient way to let the plants create a carpet. I've never tried this, but it seems pretty easy: lighting, water spraying, and some foil over the top.
I have a question here. As the tank is in my room, how do you keep the temperatures ideal? I was thinking of installing a heating lamp for 24°C (75.2°F).

I know the contrast is not ideal. What is your input on the placement of the stones? There still needs to be some lava pebbles added. The left side is going to be a little higher, and on the right, it's not completely filled.
Also, no hate on the pink quartz stones. This is what happens when you go shopping with a 7-year-old daughter. She wanted her input, so I'm calling them her hidden gemstones.

Any other advice, does and don't are welcome.

Thank you for your input.