Wide plank what? Engineered ? Sand on site. Add pictures of the existing condition. All.

The wider the plank ? The less stable the floor: )

I would not go with varible width flooring. i did that in one of my houses and disliked it. I disliked it so much i ripped it out and put wide board flooring in. In my case it was 10 inch wide boards with shiplapped edges. it was pine so it stayed flat.

i dont think narrow flooring in one room would look too bad with wide flooring in another.

Color is more important than plank width.

My 1830 house in Maine has variable width flooring- wood was expensive so they just milled each piece to the widest it could be. They range from 5-7” wide. In your case I think it’s fine to have wide boards in the entrance- that’s likely what it would have had presuming it’s in the old part. The 1930s addition has 1930s floors. I would try your keep them talking to each other by using similar wood tones.

Engineered flooring is running 7" to 12" in current engineered flooring in some species. European Oak has less open grain to allow this, as an example. Water poly in matte gies light tones with with less yellow. 11-3/8" LaGrande from Monarch.

7-1/2" Bradford Monarch.

Bona Traffic HD and Ciranova Ecofix water poly give raw wood tones not possible with oil in the past.

Thanks for your helpful replies! Here’s a closeup of the living room floor. Forgot to mention there is a library off the foyer with this same floor minus the border. So the living room would not be the only room with the 2 1/4 inch wood.

In the foyer and kitchen we will be installing solid wood plank flooring, not engineered. Agree everything should be the same wood tone. We don't really like the varied width flooring so I’m asking whether 6” or 7” planks will look weird in the foyer next to this in the living room and library.

I do not like the variable width flooring either it always looks like you could not make up your mind. I have often added new floor to a space where there is perfectly good flooring in a space next to it . A good flooring installer can do a really nice transition from one to the other but IMO the new and old need to be the same species and stain.

If the foyer is isolated from these rooms chose a floor based on the foyer (ie it has Greek revival detailing intact so wide pine makes sense) if the foyer was remodeled in 1930 and now has wide openings into the adjacent rooms that all have narrow strip floors I would probably stick with the narrow flooring to match.

@Hallett only the living room has the narrow strips and the Greek revival detailing. The foyer is open to it, to the kitchen (which we would treat the same as the foyer), and to the library (which has the narrow planks but no Greek revival detailing. So when you walk i to the house you are in the foyer, with the kitchen/family room to the left and the living room to the right. We are leaving the living room and library as is. Wondering about the plank width in the foyer and kitchen/family room.

I think the plank width is a non issue as long as all the wood is of the same type and stain.