I think I’m grandfathered in now with the railing. I don’t like the look of it completely encased in PVC railings and posts

I rolled off 100ft on level ground to my big Quercus imbricaria the measured the angle to a high fairly centered leaf with my old galaxy note and came up with 90 something feet which seems reasonable. Today I measured the mower seat height and got 44 inches. I feel decent being uphill the trees to eliminate some distortion. 44x13= 572 572/12= 47 2/3 feet for my big 2004ish vintage Arbor Day tree. I'll add this tree releaders constantly. Right now for example it has a "Y" shaped top if u can zoom in enough. 44x9 = 396 396 / 12 = 33 feet for that 2010ish skinnier version Musser Forest sourced Metasequoia I had hiding in the shade in a pot for a bit. Now I need a drone and a length of kite string to try another method.... Oh, and thank you for teaching me what a clinometer is.

There are going to be multiple ways to install new windows here, each with some pros and cons from price, to larger size/more glass, more protection against future leakage, etc. This is a conversation to have with the companies that you have quote the project for you, as the type of install can affect the price substantially. Just beacuse your home is not "new", it doesn't mean that they windows couldn't still be installed as "new construction". No accurate measurements would be needed or really even relevant by you, but again discussing the install details and the ramifications of those options -- particulalry as it pertains to the size based on your concern should provide the info that you are looking for. In the event that you are considering doing this install yourself, I'd recommend some serious research on installation methods and procedures. You really can't measure a window properly unless you understand how its going to be installed.

When I look up framing instructions, they give closet depth based on the measurement from the finished face of the back wall to the outer dimension of the outer wall studs, not the finished face. The framing plan goes from one side of one wall to the same side of the next wall, which is what you described above. The distance between those walls in the framing plan should be larger than the designed closet depth. So if these are 2x4 walls the closet width will be 4.5" less than the width on the framing plan.