A piano can be placed next to a window but you should protect it from direct sunlight. You needn't go so far as to install new windows with comfort/smart glass. Simply do what you can with the use of outside screens and inside window coverings to keep direct light away from the instrument and/or keep the piano closed/covered when not in use. My 2 cents.

Direct sunlight - Not good either for the piano case or the soundboard..
Extreme temperature changes - shouldn't be an issue assuming you keep the inside temps fairly constant throughout the year regardless of the outside temps..
Drafts - ideally the adjacent window should never be open.
Acoustics - depends on the size of the window, the type of window coverings, the position of the piano and several other factors about the room itself.

The desert heat and glare hitting the outside wall five months out of the year in the late afternoon can be quite brutal. There are sunscreens on the outside of the windows, and large wooden slat plantation shutters on the inside which let some filtered light in but which are kept closed 99% of the time. No additional window coverings are necessary. I keep the piano lid closed (to keep the dust out), and (as an extra safeguard) cover the piano when not in use. The temperature inside the house never fluctuates more than 20 degrees throughout the year. We have central air.