Narrow, site-finished oak strip flooring is the most basic classic sort of wood floors that are common in most areas.

Engineered is real wood. It's just thin layers, cross ply. Essentially plywood. It's more stable in environments exposed to moisture and temperature swings. And, it's the only thing you want to put down on a concrete slab.

I agree with Pal that narrow oak in a medium tone would be the most classic look. You want under 3". If you are on a crawlspace, doing the nail down install, site finished or pre finished. If you are on a concrete slab, you need glue down engineered. That will usually be pre finished, which is more durable, but doesn't have as much of an old home classic look. I wouldn't float anything. It makes it sound hollow. Like the fake wood laminate floors.

great advice