I would use the laptop with the lid closed and without the battery!
I think it´s a good idea to store the battery not fully charged. Perhaps, every 2 months or so you can do a complete cycle. I mean, fully charge the battery, then use the laptop with battery until it is in 5% of power (or so) and then charge it until 65% and store it.
I have never heard that power demand spikes take energy from battery. However, as almost everything in computing world, it can be measured. Download some benchmark software and run it with different stress benchamrks with and without the battery so you can test if specifically your laptop will take power from the battery. Then, you can post the results here if you want!
One more thing: in my experience using a laptop with the lid closed significantly reduced the Wi-Fi signal. That is because the Wi-Fi antenna used to be in the frame of the monitor. In that case you can use it connected to an external monitor and the with the key combination Windows key + P you can select to have image only in the external monitor.