When googling it looks like your last option is recommended.

Whatever you do, all the windows should be the same. Selectively applied muntins will look like you replaced some of the window, but not all of them.

Good read on shutters. Please size and place them correctly.

https://doorstoreandwindows.com/how-to-choose-the-right-exterior-window-shutters-for-your-home/

Historically, an original late 18th c. early 19th c house on which this is based would have had 6 over 6 in the upper windows and 6 over 9 in the lower windows if the lower sash is long enough that the divisions would be of nearly equal size in both sashes. They tried not to have obviously different sizes of panes in the same window, and also tried to have similar proportions of panes in all.

The 1830s houses I lived in were primarily 6 over 6, but if the window had a small upper sash, they were 3/6, or a long lower sash 6/9, and the top floor which had a half sized window had 3/3 so it looked like a single 6 lite sash. It was all about proportion.

When one house did a modern replacement, they just did 6 over 6 in every window no matter what the sashes looked like so the half window looked silly with 12 tiny panes in it, and the large lower sash on the first floor had 6 overly long pane in it out of proportion with the upper half of that window.

And a colonial revival house would have had 6 over one for the whole house.

Actually as bigger panes of glass became more fashionable, some 19th c houses got 2 over one on lower floors and 2 over 2 on upper windows and might still have 6-6 upstairs in the back. They didn't care about matching, it was a status thing to have bigger panes of glass.

I am not recommending this but there are some houses on a historic street where they had to replace the windows in kind with how the house was built rather than making them all the same.

All of these comments are exactly why I took the time to post! Thank you all for your thoughts and expertise!