Yep i have bought the same from the same seller before too Soldering them in isn't alway's the best idea. I heard a few year's ago that the RAAF are no longer allowing soldered joint's in their airplane's, it can make the wire's brittle at either side of the soldered joint and it doesn't allow the wire to flex enough either.
1, I don't have the correct tool to crimp them and have seen too many corroded crimp joints. 2, too much solder will cause problems as you said. I only use just enough heat and solder to stick the wire. 3, I worked on 'AEROPLANES' for many years (1975 to 1989) and they never soldered anything that I saw.
I use the crimp and solder method. Crimp on the sheath and solder the exposed copper onto the connector.
