So the conclusion that is better recharge a battery to 100% and then unplug it is correct?
Yes, just like any other device with lithium-ion batteries, it is better to charge the Surface up to 100% before plugging it off to avoid higher life cycles as Caring for your Surface battery - Microsoft Support states that "It is common for the capacity of lithium-ion cells to diminish after a certain number of charge/discharge cycles. This will result in shorter intervals between charging and lower battery capacity."
With regards to overnight charging where it is possible to overcharge a battery, under How to maximize battery health section in Caring for your Surface battery - Microsoft Support, it is stated "Batteries maintained at a high charge state will lose capacity faster. You can help prevent this accelerated process by not leaving your device connected to AC power for extended periods." that is why we also recommend avoiding charging the device 24/7.
However, the Surface has its own features also that would help you optimize the battery longevity like the Battery Limit mode (Enable "Battery Limit" for Surface devices plugged in for extended periods - Microsoft Support) which is advisable for those scenarios where the Surface must be connected to power at all times. Another feature is the Smart Charging where the device would automatically enable smart charging whenever it would detect that it needs to enable the said feature. Third feature is the Battery Lifespan Saver where it works also with Smart charging, and this would help protect your battery from the cumulative negative effects of consistent and recurrent use at high temperatures or high states of charge just like if leaving the Surface plugged in for extended periods.