As part of my research, I wanted to get an opinion on Soft-lit imperial vinyl replacement windows vs Peachtree Symmetry (Lowes)?
No comparison, the Softlite Imperial is vastly superior to anything by Peachtree.
I also had a couple of side questions on cladding and floor to window height that requires tempered glass to be installed?
If windows are a future step in a wall repalcement from masonite boards to hardiplank, should vinyl coated aluminum go on when the wall boards are replaced? I am afraid that if it is cladded now, it will have to be replaced when the wall boards are done?
No sure what you mean when you say wall boards. If you are referring to the siding, you should let the installer know you are planning on replacing the siding. The capping can possibly be done in such a way that the existing siding can be removed without disturbing the capping. You may also want to consider using a composite board like Azek when the siding is replaced. BTW, I'd use Certainteed Colormax instead of Hardi but that's a whole different discussion and one that should be adressed to the installer.
In regard to tempered glass, is the base of the windows 18 inches from the floor, the criteria for where it has to be specified?
Glazing in doors and enclosures for hot tubs (both inside and outside), whirlpools, saunas, steam rooms, bathtubs and showers or any part of a wall enclosing these areas where the bottom of the glass is 60 inches or less off the drain, needs to have tempered glass.
If a window meets all four of the following criteria the glass needs to be tempered.
a. Exposed area of an individual pane is greater than 9 sq. ft.
b. The bottom edge is less than 18” above the floor.
c. The top edge of the same piece of glass is 36” or more above the floor.
d. If one or more walking surfaces are within 36” horizontally of the glazing.