solid wood is 3/4" thick. You can sand down to where the nails are which is where the 'tongue' is. Engineered wood is 3 5 or 7 plys with a veneer of hardwood on top. Its generally more stable than a solid. There is no intrinsic advantage of a solid over engineered, though there is a perceived difference as one is 'thicker'. That has really nothing to do with anything. Factory finishes are generally far more durable than anything you can do on site. Unfinished allows you to stain any color and sanding will make the floor real flat and smooth. Prefinished you can't pick stain color other than the std colors, and generally will have overwood if the floor isn't perfectly level. As anything in this industry there are tradeoffs to all flooring materials.

Even without knowing the kind of wood or condition, I can't imagine replacing wood flooring in an 1890 home. In my opinion, the value is in the original material. If the floor is in good condition, it may not need sanding at all; a screening and recoat might be all that's necessary and the patina would be retained. There are many threads on this topic, try searching the Old House forum. I live in a converted schoolhouse built in 1890. The fir floors had been covered with layers of linoleum, glue, paint ... they were a mess.. but looked awesome after refinishing. That was years ago and I'm planning to have them screened soon (aka buff and recoat.) What kind of wood is it? Do you have photos?

When it comes to "trends" vs. "timelessness" you want to look at your personal timeline for selling. Are you planning to sell in the next 5-7 years? If so, go with the trend and ignore your own tastes. If you sell in a few years then you are not buying/constructing the home for yourself. You are creating it for the NEXT buyer. If you are in it for the long haul (7+ years) then you put in the floor that makes YOU happy and that makes YOU smile and that makes YOU feel better about your choices. If you want flooring that can be "extended" into other areas for a later remodel (like in 10 years time) then work with the 3" product. It will be around for a long, long, long time. Wide planks are trending HEAVILY right now. They come and go. And if you are in there for 10+ years, you will want to have the option of refinishing so that when it comes time to sell, you can update your floors for $5/sf instead of having to pay someone to rip out and replace the floors ($10+ per square foot for a job like that).

I would recommend looking into buying from LL Flooring. They back their product and the flooring is spicifically desgined for their company. If you decide to go with Shaw or Mohawk from a distributor, read the warranty and product return policy. Unfortunately, I found out the hard way that Shaw nor the distributor back their product and nulled the agreement based on the flooring going down before the painting was done and applinances installed. Weird… yes, and our flooring was covered in Ramboard the entire time. and I have pictures. The appliances had nothing to do with the flooring in the dining room, living room and upstairs. Bottom line is a big manufacturer isn’t going to take responsibility.