Soldering is not difficult, but it requires technique. We can explain the technique when you have something to solder. I'm an electronics teacher teaching 11 - 16 year-olds. All the 11 year-olds I teach can solder. Those that listen, do it well, but all of them do it well enough for their products to work. To solder, you need a soldering iron and some solder: total cost is about £10 to £15. When you use a DIY ebike kit, like the one from BMSBattery, you have to solder connections on the the battery wires. Everything else has connectors already, but you might need to extend the rather short pedal sensor wire by cutting it and soldering in a longer piece.
The Ezee kit would be more or less plug-and-play. Although it has latent power, what you can buy ready-to-fit has nowhere near the power of the BPM kit.
Torque arns are nothing complicated. They fit over the axle and are clamped to the frame, which makes a reinforcement to stop the axle twisting out of the drop-outs.
EBike Torque Arm