Depends on the house style

Grilles or no grilles are a matter of personal choice and the style of your new home. I had the same decision to make. I looked at the houses in my neighborhood and other new construction. I found that most of the windows had grilles. I opted for large windows with fewer grilles/larger panes of glass.

The style of window, number of lights and style of mullions is very important to the character of your home. There are egress codes that also govern sizing in bedrooms, ans safety issues when the sills are low - requiring more expensive tempered glass. casements, awning, single and double hung, sliding, sliding and french doors - aluminum v vinyl v wood v clad wood - all of these have different insulation factors. cross-ventilation can save you big $$ on cooling - these are all factors to consider.
if your house is uber modern, then no grids but the layout of operable and picture (non-operable) and sizing / massing indicaten that style - for mid century, aluminum that maximizes connection to the outdoors / sliding soors are period appropriate. If your home is traditional, then a great look is pairs or trios of single or double hungs with cottage grids only on the top half - a custom look for less. If your house style is craftsman, you should search craftsman exteriors here on houzz to borrow style points from the high end homes. you may see use of more transom lights / grids if you are spanish/ meditteranean, casements with horizontal only mullions are high end - sometimes flanking a picture window. large arched top and eyebrow top windows send different style messages. Windows are the eyes of the house, therefore the soul. so put in the house style you were going for - search houzz exteriors and make an ideabook. My best advice is to get as many lights operable as possible - unless you live in the desert. fresh air is a terrific asset to a home;

Grids or Muntin bars play an important role in the overall detail of a house. As stated above the grid pattern depends on the style of the house. I do not see them going out of style.