Experiences with insulating a tiny house from the outside?

[*]13 mm spruce three-layer
[*]Vapor retarder (is it needed?)
[*]4x6 KVH with 6 cm stone wool insulation
[*]Vapor barrier
[*]20 mm vertical battens (ventilation)
[*]20 mm rhombus profile

Ceiling, from inside to outside:

[*]13 mm spruce three-layer
[*]Vapor retarder (is it needed?)
[*]4x20 KVH with 20 cm stone wool insulation
[*]Vapor barrier
[*]20 mm vertical battens (ventilation)
[*]Roof made of trapezoidal sheet metal

Would this construction be correct?

A vapor barrier on the outside is basically wrong in a "normal" house. Therefore, I would think it is also wrong for a tiny house.
The vapor barrier/retarder must always be on the inside of the insulation layer.

If you don't know why, where, and how to install a vapor barrier foil - better leave it out. Inside OSB and outside on the insulation a vapor-open underlay membrane to ensure wind tightness and that's fine. Inside OSB glued well and seal all joints and penetrations. For example with acrylic or sealing tape. No drafts inside / nicely airtight. Inside three-layer battens are also possible, just no tongue and groove battens - they are not airtight. 16cm floor insulation is a bit generous. If you need the 16 cm for the statics, okay. Otherwise half is enough.

The vapor barrier must be placed on the inside before the insulation. On the outside after the insulation comes a diffusion-open but windproof foil (e.g. windpaper).

You can also use OSB boards inside instead of the vapor barrier and tape all joints/seams with adhesive tape. However, I would then install a thin visible cladding in front of it. Also pay attention to penetrations of the vapor barrier for electrical and sanitary installations. The solutions have to be planned in advance (you don’t have to invent anything new, just choose the right solution).

For the insulation, due to the small thicknesses (for the floor I would also use fewer cm), I would use high-quality insulation wool/boards. Nothing with a lambda value (=thermal conductivity, smaller is better) of ~0.04 but closer to ~0.03 W/mK. --> gray instead of white EPS, better insulation wool, better XPS, PUR/PIR insulation...

Good insulation and ventilation also help you against overheating in summer.

Is a wood stove or heat pump/air conditioning planned as heating?