Answers

I suggest take a look at the ProVia Endure high grade vinyl window. 

Triple pane is what I sell now and has very low U-factor and air infiltration.

I love their low profile slim casement window, just amazing.

The quality is nothing I seen before in my 22 years in this field.

Available in new contruction nail fin.

https://www.provia.com/productdetail/vinyl-windows/endure

Installation is very important, good window + poor installation = Problem.

Cost varies from contractor to  contractor. Check with your local building supply stores that carry ProVia products (not HD and Lowes) or go to PorVia to find a dealer. 

Suggest you request bids from several dealers and supply stores with the same specs

Best wishes

I strongly suggest go to James Hardie wedsite, download their installation instruction and get familiar with the process. We witness so many fiber cement siding that was done wrong. It may be wised to have a clause in the contract that the work will be done according to James Hardie's installation instruction.

Problem may not arise in few years and contractor's warranty on paper is a joke if he has no intension to honor it.

I totally agreed Mr. Jim Myers' suggestion to check on the contractor throughly.

The key is doing the job right the first time will save you a lot of headach down the road.

Good luck with your project.