Insulate the windows with fiberglass

This is not meant to be a complete answer, but might help with your understanding of it. My understanding of the physics of windows is as follows -

Nearly all radiation (visible, UV, infrared, every other type too) that travels from outside the house into the house and is absorbed (not reflected back out again) is converted into heat. I would expect that exceptions (such as the energy from UV light causing a chemical change, such as when it fades your couch, or waves that induce a current in a conductor) are relatively negligible.

This means any radiation that can be reflected from the window to prevent it entering the house reduces the heat load. Also, if the radiation is absorbed into the window glass (eg through tinting it), then some of the heat from the window glass will be lost to the outside (through both conductance/convection and some radiated heat) which is an additional benefit.

A heated window pane would like lose more heat to the outside than the inside because the wind would help keep the temperature difference between the glass and the adjacent outside air larger than the temperature difference between the glass and the inside air.

Using LBLs solar gain modeling software (RESFEN) can be instructive. I don't know if they have finally made a less cumbersome version of it yet - last I used it it was still Windows-only and ripe for redoing as a web app. Looks like it's still stuck on Windows PCs only. There are few other tools there on the page linked to as well.

E&W actually have more summertime gain than S (northern hemisphere - swap north for south if on the other side of the equator) due to the solar angles being low during the morning and evening. South windows are more easily made seasonal with shading that keeps the sun off them in summer and on them in winter.

If blinds are on the inside of the window, the heat is still inside the house, with the blind that stopped the sunbeam - exterior blinds or awnings are needed to really keep heat out with a shading product, AFAIK.

I think the most effective way to make use of solar heating for winter is to separate it from your windows, using dedicated collectors. In addition, it's actually become quite difficult to source windows that are good heat collectors (I do understand that what you are really doing is choosing between levels of SHGC - but I wanted some high solar gain but well-insulated windows for my south facade and ended up giving up, as the only ones I could find to buy would have been importing from Canada at 3 times the cost of the low SHGC windows that were all I could get locally - in a mostly-heating climate.) I can build or buy solar collectors with the cost differential I would have had to come up with for the windows I wanted as opposed to the ones I got.