fvwm2 may work for you. With enough effort put into configuring it and its modules, you may get almost any look-and-feel. Depending on what do you mean with “N

fvwm2 may work for you. With enough effort put into configuring it and its modules, you may get almost any look-and-feel. Depending on what do you mean with “NeXT philosophy”, Window Maker and the whole GNUStep suite may also be worth checking.