Hi dear @stef1, I think you know the answer to those questions, you already have experience in watercolour.
Anyway, as you know, the paint must be wet when adding another layer so that the new one follows the same path, otherwise, the colour will expand outside the initial layer.
In watercolour, the trial and error method is crucial to know how, when and with what load we can apply the paint. This is something difficult to explain verbally.