So long as the iron works, it should be fine. What is the wattage?

TBH, I don't solder connectors these days without a third hand, makes things that much easier to do. The presoldered one you bought will still be useful. If you cut off the banana plugs, like you mentioned, they become pigtails and easy enough to solder into a wiring loom. That is what I did before getting to grips with a third hand.