I think I'm going to leave my floors their natural color and put an oil/wax finish on, maybe Rubio Monocoat. I water-popped an out of the way strip to see how it looked wet and plan to test some jacobean stain on it later. I really like the color it turned when wet, maybe just a tad darker. ( 1 ) How would water-popping affect the finish without staining, especially if I were to use a clear rubio monocat or some other oil/wax finish? I really like the depth the wood showed when I wet it. It had a 3d look to it. I'm looking for a matte/satin finish. I'm not into glossy floors but I wonder if a matte/satin finish would remove some of the depth the floor showed when wet with plain water. ( 2 ) Also, anyone have any idea what kind of wood this is? It smells a bit piny when sanded. Lots of red/pink boards. House built in 1925 Memphis, Tennessee. Heart pine? Douglas fir? Mixed maybe? They are lonnng, 12 or more feet. ( 3 ) I'm not sure why the grain in the board on the left has lightened up and the 3d looking board in the middle seems to have darkened the grain versus the mineral spirits used on the two boards up top. Could that be a chemical reaction with something in the tap water or is that just how raised grain looks? (I know I'm supposed to used distilled water) ( 4 ) Can I expect the same results/color you see in the photo with the water-popped and non-popped mineral spirit wiped boards if I used a clear coat monocoat or some other oil/wax finish? I like 3d effect of the water-popped board but not the lightening of the grain in the board left of it. I'm hoping the finish would darken that grain back like it is when wiped with mineral spirits without losing the more pronounced depth in the middle board. This is my first time doing anything like this and really REALLY don't want to sand it again lol I drum and edge sanded 36-60-80 (was planning to stain) then went over it with a home depot orbital at 80 grit, ( maybe I was supposed to use 100?) vacuumed and tacked, went over any swirls/sweat stains by hand with 80 grit sand paper and will clean with mineral spirits and catch anything i missed before doing the finish ( or possible stain/finish) Not totally dead set on on oil/wax but like the more natural flat look of it. One more thing, an enormous 375 pound person ( I think he may weigh more) visited my house and now a few of the boards sink down when stepped on. One of them even cracked in the middle ( sigh) ( 5 ) What type of wood would you recommend to replace that board? Any pine/douglas fir with the same color and grain pattern? ( 6 ) About the boards that sink down when stepped on, do I just need to go into the crawl space and reinforce them? They are nailed directly into the joists, no subfloor. Thanks for the help.

Your floor looks like southern yellow pine to me. The better grade will have all vertical grain, which is also called quarter-sawn.
Yes, go under the floor and reinforce it with some blocking.
I recommend one-half inch plywood cut into two inch rips glued with sub-floor adhesive, a quarter-inch bead in the middle of the strip, and held with one inch sheet rock screws until the glue sets. Place the strip between the floor joists and be sure to pre-drill holes for the screws to go into with a 5/32nd inch drill so the screw can suck up the strip when you tighten the screw.
Oil finishes usually are harder to keep clean than a surface film type of finish that las a wear layer.
There are film types of finish that have the matte look of an oil finish.
Ask someone who has had an oil finish on their floor for a few years what they think about it. I wouldn't recommend it for a kitchen.