Who makes an independent and professional electrical plan?

The planning in a single-family house is usually done by the electrician, as there is hardly anything to plan; it is not an airport terminal or theater. However, as you were already informed earlier, there are also lighting planners, IT planners, and system integrators for the somewhat more demanding customers. It is like with the kitchen. You can go and have it planned by the consultant in the furniture store or by a specialized kitchen studio. Both somehow do the same thing, but there are differences and nuances.

That would then be someone different than the electrician? Ok. Do you have any idea how this works and what costs I should expect? A quick Google search gives me everything from "Online light planner free" to great lighting installations in event centers...

I would recommend that you find a lighting planner or lighting consultant, who is usually connected with kitchen manufacturers. We had kitchen lighting planning included in our kitchen offer. We asked the same person to take care of the lighting planning for the whole house. Typically, the consultation, sketching on our floor plan, and providing documentation costs around 200 - 300 euros.

[*]what are the pros and cons of planning by such a provider?
[*]what is the typical cost range (single-family house without much frills)?
[*]which companies can you recommend?

Pro (for a single-family house without much frills): -,-
Contra (for a single-family house without much frills): price, necessity

This also applies to water, sewage, etc.
All of this is included in the price of the craftsman.

For a standard single-family house, I would only have the heating design (room-by-room heating load calculation, hydraulic balancing, underfloor heating layout plan) done by an engineering office for around +/- 150-250€.
Light planning is debatable, but it is often offered for free or for a small fee in lamp specialty stores (however, you can also read up and think about it yourself).