No autosizing of equipment on proposed?

1) yes. the leed process requires the proposed model to match the design documentation of the project. For initial testing of your model, or at early stages before the design documentation is finished, you could start with autosized values, but these are not for submission. 2) i use energyplus. in energyplus, you define a seperate set of schedules that are used for the load calculations when running the sizing simulations. sometimes these schedules are the same as used for the annual simulation, but for some items like occupation, they are not...they are also different for the heating load simulation and the cooling load simulation. 3) if your innitial question is about fan power consumption at different flow rates, then the answere is beyond the scope of this forum (hint: the flow impacts on the hydronic pressure that the fan must overcome in the system and directly impacts the power...check out your software's user forum).

Appendix G requires that you model the building as designed. It the capacities and airflows are autosized and only slightly differ it is usually not an issue. It is when they differ by a wide margin that it can affect energy use. Most modeling software is not used to size equipment.