Position of electricity meter on wooden stud wall

If the electricity meter is to be installed in a different room than the main connection, there are generally problems with the supplier. The main line may not be routed arbitrarily underground with my supplier, and the voltage drop over its entire length must not exceed 0.5%.

The electricity meter will be installed in our hallway; it is just a small house without a separate utility room. The water meter will be in the bathroom; I had a similar question about that.

Yes, placing it in front of the wall makes more sense to me as well. That would also give us the option to insert crossbars into the timber stud wall to attach the fuse box.
Possibly, I would omit the gypsum fiberboard at that point, go directly onto the OSB, and then "enclose" the fuse box with multiplex boards or similar, equipped with an inspection flap, and hang a mirror in front of it.

The mirror would then have to be at least 55cm wide and 110cm high; that would be the size of the meter cabinet.

Maybe I would skip the gypsum fiberboard at that point, go directly to the OSB, and then "enclose" the fuse box with multiplex boards or similar, equipped with an inspection flap, and hang a mirror in front of it.

No no, the gypsum between wood and electricity does make sense.

As described above, the single-circuit cable entry for electricity is in the same position as the fuse box. The question is only at what depth the entry should be set. We have a slightly larger box for optional future consumers (meter for photovoltaic system, meter for wallbox, etc.), so attaching it only to the OSB board does not seem ideal to me. Primarily, the question for me is, where should the main cable that goes into the fuse box and the cables that go out to the sockets/switches be routed.

1. In the partition wall
2. On the OSB board (without gypsum fiberboard and installation layer)
3. Between OSB board and gypsum fiberboard = installation layer
4. On the gypsum fiberboard

You can do it however you want.
Photovoltaics up to 9.9 do not require an extra meter, only from 10 kWp.