Sockets go where you will use them
Russian code SP 256 asks for at least one socket per started 3 m of a living room's perimeter and one per 10 m² of hallway. A 3 x 4 m room with a 14 m perimeter gets five. The code doesn't say where they go, so the app spreads them across different walls and stops at six per room.
A socket won't end up behind a wardrobe or a sofa, because it is placed after the furniture. Behind the fridge, the washer and the TV it is left on purpose, since the appliance plugs into it. An ordinary socket stays at least 0.6 m from the sink, bath and toilet. Closer to water only a splash-proof one with a lid goes in.
Socket circuits are always 16 A
To estimate the load on the apartment's supply, each socket counts as 300 W. Yet any of them may get a 2 kW kettle, so a socket circuit never drops below a 16 A breaker on 2.5 mm² cable, and lighting runs on 10 A with 1.5 mm². Cable is sized to the breaker because the breaker is there to protect the wire. Put 25 A on a thin cable and the wire overheats before the breaker trips.
A socket circuit holds no more than 8 points or 3.5 kW. The washer, dryer, dishwasher, oven, hob, water heater and air conditioner each get a dedicated line.
Water and the kitchen go through 30 mA protection
Bathroom and laundry sockets form their own circuit behind a 30 mA RCD, a device that cuts the line when current leaks where it shouldn't, say through a wet hand. Kitchen sockets go through an RCD too.
Every dedicated appliance line, from the washer to the oven, gets an RCBO. That is an RCD and a breaker in one housing, and it takes two modules in the panel instead of three for a separate pair.
The enclosure leaves room to grow
Devices go in the order an installer would fit them: main breaker, voltage relay (it disconnects the apartment on a mains surge), RCDs, circuit breakers. Panel size is counted in modules, each a 17.5 mm slot on the rail. The enclosure comes from the 12, 24, 36 and 54 module range with 20 % spare. If the devices take 25 modules, 30 are needed with the spare, so the app picks a 36-module box. A panel filled to the brim has no room for the water heater you add next year. If the circuits don't fit into 54 modules, the app tells you a second panel is needed.
You can override the calculation
Three-phase supply, an extra appliance or your own circuit grouping can be set in the Electrics panel, and current, cable and modules are recalculated by the same rules. Cable length is estimated along the route from the panel to every point.
The result is an estimate for budgeting and for a concrete talk with an electrician, and the panel sheet says so. A design for sign-off comes from a qualified electrical design firm.