Unfortunately that's hard to answer. There are some builders that yes there are gas lines and if the builder or original owner chose to put gas in the home it'll have gas, but then there are some builders (like mine) that didn't offer it as an option and we had no choice but to go electric so it will depend on your individual home that you are looking at and possibly making an offer on (not just the builder but each individual home will be different).
On insulation that will depend on what the original owners did. Each home builder has their standard insulation and it's up to whoever built the home (the original owner) to pay more money to insulate more. We personally spent more than I'd care to remember to insulate to the hilt, but it helps on our electric bill in the summer. So that would again depend on your individual home that you are looking at and cannot be said with any accuracy across the board or even with the same builder as each owner had the option to upgrade their insulation if they so chose. If you end up with a home that has poor insulation they now make that spray foam stuff that you can do your own insulation which I have heard WONDERFUL things about and it's fairly simple to do.
So bottom line answer to both of your questions...it'll depend not only on the builder that built the home (there's a few different ones that built in Castlegate) and it'll mainly depend on each individual home that you look at (and that's really anywhere you go).
Good luck!