Anderson makes a window (woodwright series) that is vinyl clad on the outside and wood on the inside.

To get unconfused you need to ask your builder for more information about the windows he has proposed and then tell us what they are.

White sash and frames will look OK with natural wood trim if the general style of the window is informal and simple. I have never liked oak as a trim material because the grain is so coarse and I also suspect it might be too formal for the white sash. I recommend using a different wood like mahogany or red birch.

Also, creating three very different material/finishes at the windows (wall, trim, and sash/frame) might look odd.