Energy simulation for a residential house using Ideal Air Loads system

Hello to the team,

I have been reading a lot of the posts in the forum regarding the Ideal air loads system, because I have some trouble understanding the results from E+ simulation.

The schedule with the heating setpoints is attached below.

We set the ventilation rates (sum of the flow/area and flow/occupants) using Loads component and we also set also the ventilation schedule for each zone to supply the air volume needed based on the presence of occupants.

Moreover, we set no economizer.

When the energy simulation ran (for 20th of January) using OpenStudio we get 3 nodes for supply air temperature while we get an hourly supply air temperature if we use EnergyPlus. I think the two first nodes correspond to the supply and exhaust air while the third one is the outdoor air inlet (and it is max 50degrees as the default, related to the air temperature coming out from the heating coil when the heating system is on). Is this correct, otherwise can you explain where exactly are these 3 nodes?

I expected that the supply temperature would be close to the heating setpoint and not to 21oC (which I do not know why it comes from). It seems the system supplies the zone with variable volume flow but at constant supply temperature (which is the same with the indoor air temperature). I expected the opposite since in 2019, when I ran energy simulation with EnergyPlus for a single zone, the system moderated the supply air temperature and kept the volume flow supplied to the zone constant. This is more energy consuming, but does this happen because maybe it was default like that back then?

In the picture below, during noon, the operative temperature rises above 23oC, possibly due to solar gains and of course, heating is off. At these moments, the minimum volume flow is supplied to the zone and the third supply air node temperature drops close to zero (makes sense). However, the supply and exhaust air temperatures are getting high at these hours. During rest hours, the volume flow varies. Why?

I would appreciated if you can enlighten me because I am struggling to understand how it works and to figure out if i have set a right workflow for the system here.
Thank you so much in advance!!!