Looking at the Caldercraft, advert it rather depends on how much detail is already shown. If you don’t like the detail (including rubbing strakes) then you have the option of sanding the hull smooth and then applying your own plating and rubbing strips, perhaps using card or 0.4mm ply and adding rivets using a hypodermic syringe and PVA glue. Quite a fiddly job.
You have to ask yourself what is the best compromise between realism and practicality. The model as it comes has a degree of representational detail which might not be strictly correct but looks the part and would be accepted by most viewers,albeit not by yourself. So you could spend a great deal of effort in making corrections that nobody else but yourself will notice, especially at the distance that the model is viewed on the water.
Moreover, the kit itself will have other compromises over a strictly scale depiction for commercial reasons as is pretty much normal.
If you want a model which is a true to scale as is possible then building from scratch is probably the best option rather than trying to modify a commercial kit which inevitably incorporates compromises for sound commercial reasons.
In reality the differences in some cases my be not all that great, especially as viewed by the average onlooker.
As always, horses for courses and you only need to satisfy yourself.
Colin