Power output as heat:
Presumably, that 0.95 refers to the lightbulb being 5% efficient. However, that is incorrect reasoning. Efficiency does not refer to how much is turned into useful work instead of turning into heat, it's how much is turned into useful work before turning into heat. If a lightbuld produces 95W of heat and 5W of light, that light is eventually absorbed by something, and that something will then be heated up. So all of the energy of the lightbulb eventually turns into heat. Pretty much every use of energy eventually turns into heat, with only a few exceptions (an example of an exception would be that any energy used to build a skyscraper that goes into lifting building materials doesn't turn into heat ... at least not unless the skyscraper is demolished), and those exceptions are a tiny percentage of energy usage.
The atmosphere has a mass of about 5.15×1018 kg (Wikipedia)
specific heat capacity of air:
SHC of air 0.716 https://www.ohio.edu/mechanical/thermo/property_tables/air/air_cp_cv.html
Both the mass, and heat capacity, of land/water is much larger than that of air, and for air to remain at a high temperature, the ground and water below it has to be brought up to that temperature. You can have a region with cold ground and warm air, but for that situation to persist, that warm air has to be coming from someplace else that does have warm ground/water.
Small amount for what I feel is still a gross overestimation of 100x 100W lightbulbs per person as an internal energy output, but why isn't this a factor especially as the world becomes more energy hungry?
Besides this being a tiny proportion of the total heat, it's not permanent. The main concern over CO2 is not that emitting CO2 in 2019 will make the Earth hotter in 2019, or even 2020 or 2021, but that all the CO2 emissions are cumulative, and thirty years from now we'll still be dealing with the effects of CO2 emissions from today. The urgency of anti-warming activists is based on the premise that global warming has a lot of momentum, and it will take a lot of time to turn around warming trends. Simply adding heat to the system, on the other hand, doesn't have the same long-term effects. Heat causes objects to radiate heat. Without the greenhouse effect, raising the Earth's temperature means that it radiates more heat, and so without a constant influx of new heat, it will cool back down. So even if we were to raise the Earth's temperature by turning all our heaters on full blast, this wouldn't be a threat to later generations the way that CO2 emissions are asserted to be. CO2 reduces the amount of heat that the Earth emits, and so can permanently increase the equilibrium temperature.
Is it 'heat neutral' I find it hard to imagine that something even like a wind turbine generating the electricity would decrease the heat energy in the air more than an electric heater powered off of it would.
If you stick a heater next to wind turbine, all of its energy is coming from the energy being taken from the wind, and all of that energy would have turned into heat anyway (see my first paragraph). For the heater to result in a net increase of heat would be a violation of conservation of energy. Same with renewal energy in general, such as solar, geothermal, hydroelectric, or wave.