Block or poured basement walls, that is the 50-50 decision and both have pros and cons...have built and lived in houses with each...
Rec'd some decent 'mat like' barrier for exterior wall, below and up to grade on either choice of basement wall construction. Goog has dozens of links, your builder should have decent rec'ds, product wise.
They are not 'bullet proof' but they help and should not be skimped or skipped, imo.
Pipes: We have PEX, installed 23+ yrs ago, and our water piping system has run well. Only snafu was builder used 'pieced' PEX from street water box to house main entry, and that pieced long run failed/leaked a few years ago. If your street 'water box' is a long run to house they do sell one piece pex in v long spools.
We lived full time in our Waynesville Mtn home from 2001 to 2005, with serious azz winters back then, at our high elevation: never had a pipe 'burst' or leak due to cold temps.
Be sure builder puts inside 'main' shut off valve that is accessible, and the street 'water box' should also be v accessible, as most of us turn that off when we leave for more than a few days.
Outside spigots: our builder installed Woodford brand spigots...they still work and have never frozen.
Don't chinch on quality or number of outside spigots.
Some builders will offer an additional outside above ground single 'full pressure' spigot for garden use: they can really crank the water volume/pressure vs the pressure reduced through wall outside spigot. Maybe one in front and/or back yard.
Have some decent electrical outlets/potential lighting switches run in basement and or crawl space. A couple few awning type windows in basement wall(s), if some of basement wall is above ground.
If 'mechanical', eg heat source/water tank et al are in basement, give some thought to where, access, and 'disguise' or 'hide' vs builder just placing them where it's 'easy' for him/HVAC subcontractor.
Basement and pipe stuff that comes to mind...
We are all spending your $.