Your installer will have brands and sources available locally. Do not go outside them. Source with them. Or you hold the responsibility for all the problems.

Wider boards may be susceptible to warping more than a thinner one. The type of floor that it is going over may be something to research, like heated cement, or heated or unheated crawlspace. Just questions that come to my mind. We are building new also and I would like wood floors.

I am looking at buying the wood directly from the sawmill. A local shop has birch. We used 3/4" thick, and staggered the width. 2-3/4" wide and 4-1/2" wide. So it doesn't appear as mechanical to me. Our new home has in floor heat so I would use 3/8" thick birch or white spruce. Our local wood. And the same widths.

As a woodworker for a long time I have noticed that if you make something that is a bit different or has something built into it that folks will take a second look. Your special bit of uniqueness.

Maybe try and research your local sawmill and think just a bit out of the box. Try to stay with your roots, what you want exactly any way you go and never look back.

I'm sure you will have a fabulous home whatever trail you take

I recently installed my own engineered european oak, and as a hobby woodworker I felt comfortable in selecting and installing the wood. But your question can be a bit open ended depending on what you're looking for in the higher price ranges. There are a couple things to be aware of. Firstly, as @DeWayne said your installer may already have a source or sources they're used to working with. They may be unwilling to go outside their usual sources (and understandably so). So you may wish to speak with them first. If you select your own floor and something goes wrong with the order or install the fault may land on you if you go outside their recommendations.

If you are free to chose your own, the first thing I would caution against is going with a big box store or chain. I looked at samples from places like Floor and Decor and Lumber Liquidators just out of interest. What I found was that their highest end products looked suitable but were no longer any cheaper in that range relative to direct from mills, so at that point you're better off just working with a small supplier. Plus their wear layers then to be on the very thin side. Ideally you want a wear layer of at least 3mm to have the depth of real hardwood. Even if you don't ever refinish, a paper thin wear layer means any slight damage to the floor exposes the plywood underneath.

In all my searching, I can't think of any I saw in the $20 a sqft range for just the bare floor. The only one I know in that range is in the house of a friend of mine who is a custom home builder and used hand scrapped prefinished engineered hickory at the cost of $20 a sqft. If you order directly from a mill you can find nice flooring in the $6-12 a sqft range. I ended up using flooring from Hurst Hardwoods, 5/8" thick by 10 1/4" european oak and was really happy with it. If I didn't go with them, I would have ended up choosing Sawyer Mason, which isn't available in all parts of the country but since you said you're also in the Northeast you may find a local dealer. Theirs was like walking on a piece of furniture, and still in the $9-12 a sqft range.

Currently, engineered European or French Oak Q. robur in wide planks is available from a large number of sources. Here's an article for info.- All About OAK - monarchplank

It's a different species from N>American White Oak. Less yellow without the open grain. This means you can flat cut the veneer for more detail in wider sizes.

These are from Monarch.

Of course, you have to watch out for Chinese products using Siberian and other oaks.

I'll second that Monarch is also a good brand, but I wouldn't say they're the best value since they're typically distributed through retailers that have their own markup since a middleman is added. That being said, you do know you're getting a good product, and your builder or installer may get a discounted rate with the retailer.