The reason I use plan then implement is because I can adjust the plan, whereas if I get it to implement straight away, it might (and often does) make the wrong decisions that will be harder to adjust, or I'd have to adjust it after the fact.
I still use a plan, because my local model is not as smart as opus, but I can iterate much faster.
Once you've done with the pieces, do one "integrate them together" part, then you have a fully formed plan with less chance of wrong stuff in it. Yes, this requires a bit more interactivity than "prompt model then come back after making and drinking a coffee", but personally I prefer that.
I tend to use 5.6-Sol now more for one shot type of tasks where all I want is the answer and I’m not going to read the reasoning.