I like many of your comments about improving Windows 10, but the press to select a character is not one of my favorites in the Mac. I write in Spanish and English and use both platforms (and Linux). Having the ability of using dead keys to write tildes and accents is a lot quicker when you are touch typing than pressing-waiting-selecting.
I prefer in Windows to set the Keyboard to English International when I am typing in Spanish on an English keyboard. In this way I get the dead keys to type accented letters without relying to get them through the ALT-number method. The method of using Command-E and Command-N for accented letters is fine on the Mac, but I am a lot quicker with dead keys.
Sadly, there are some characters in Windows still rely in the old ALT method, namely the inverted ? and ! that are used in Spanish. For this I can see the case for having the long press for special characters being that these are not used often compared to accent or tilde.