I get where you are going with light weight and if I had the money (and was a little younger...) I would jump right into the seat of one of Velomo's light sports quads. But I drove a heavy trike in the Basque Country for a few years, a 20/26 T-Tris 26 from Azub. Without motor, with e-assist and then without again. I did not buy a KMX at the time because I had heard bad things about the steering at speed.
I was able to go places with the trike I would not even think about going on an upright and with the stock 3x8 gearing climbed >10% gradients regularly. The LBS owner said I had even managed >20% on one of my rides, it took me a while but I got to the top.
Stats:
- 30 km/h average over a 28 km flat route up the river and back when I was fit (including a section on cycle paths in town)
- 70 km/h + on the long downhill on the main road to the Spanish side (I learnt not to touch the brakes there)
- you learn the side-car cornering technique, on 2 wheels and hanging off the seat, the Col de St Ignace was a lot of fun
So my list:
- 20" wheels on the front with light, folding BMX tyres, Michelin even make tubeless. Rims as wide as possible.
- 26" rear wheel with a 28-559 Conti Grandprix on a wide rim
- 1 x 12 gearing 10-51 GRX for example, then up to you to choose between the 34 or 50 ring manually without a front shifter depending on the terrain. You will probably need a system to take up the chain slack. My guess is that you will drive most everywhere with the 50T ring.
Of course all of that is out of budget but I didn't have one when I bought the trike either. Or when I built my first vélomobile

You just have to decide what you need to do in your life...