If this is showing the 1990's addition this is very strange. It's as if they wanted to use some reclaimed lumber and forced the sizes they had on hand into a design that makes no sense with regards to layout or structure. From these pics, it doesn't appear that the floor sheathing is used in any capacity for a floor diaphragm, so you could remove the planking. I would also rethink what the space above is used for, if at all, and how the space below is affected by the haphazard beam layout.

Thank you!! It is, yes! The larger beams that look more like support are from a dairy barn that used to be on the property, but the catwalk looks almost like floor boards that click together? The previous owner used it for storage. There's an attic space bump out that connects from our garage (behind the fireplace) but there's nothing else up there. There's so much storage elsewhere that I don't think we'll miss it, plus it looked cluttered when we toured the house initially

Good feedback and glad you picked up on my subtle terms "if at all" and "rethink." It seems you would see anything stored up there which I agree would be weird, and it looks like the skylights and fan light creates strange shadows. The haphazard short "floor joists" create a weird pattern, and I would question the size of the 2 beams that support those "floor joists" as being adequate for dead and potential live loads anyway. You have a striking fireplace, so to open up the space and maybe unclutter some of the beams might match the opportunity you have there.

The Tongue&Groove floor planks, and beams too, if you don't have another place for them they fetch good $/board foot in the market.

Thank you so much! I really appreciate your considerations!