Find another dealer. I have always considered replacement windows as something that is made to fit in any frame. Unless the frame size is the same for both your current and new windows, I don't see how they would fit.

Perhaps the wide blinds won't fit because the new window is wider than the old window (mainly because all new windows these days are double glazed.)

As for LoE, it is a coating that lowers the heat transfer and retards the solar heat gain (i.e., the sun coming in and heating the home - which although good in the winter is very bad in the summer.) The glass manufacturer is probably Cardinal, which makes a number of LoE glasses - 240, 270 & 366. The last two digits are the visual light transmittance in percent (the lower, the more shading.)

The 366 seems to be the best glass for any window that would get the summer sun, as it has the best solar heat gain retarding with a good light transmittance (good for east & west.) The 270 is the cheapest, but has low solar gain retarding (good for the north, or south, if the eaves are long enough.) The 240 is almost like a tinted glass, and nowadays is really only put in by cheap contractors who don't want to pay the extra for the 366.

Argon or Krypton (or any noble gas) lowers the heat transfer even more - but not enough IMHO (at typical dealer prices) to make it worth it. Besides, evidently the gas bleeds out after a few years, being replaced with plain air, which is about 3/4 Nitrogen and 1/4 oxygen (both diatomic molecules which result in a higher heat transfer coefficient than the noble gases.)