Particle board subfloor - cover with additional plywood/osb for luxury vinyl plank flooring?
particle boards don’t tolerate well humidity so remove them if your place can get humid. They will fail and whatever you put of top of them won’t be properly supported.
For subfloor, both plywood and OSB will work fine.  Many use OSB because it is much cheaper and the appearance is not a factor.
If you plan on stacking boards, always overlap the seams for more stability.  Align the seam near the center of the board above.
If you put a board on top of the existing PB, make sure you take in consideration that you floor is now raised. For example, you might have to trim around door casing.
1/4 board is okay if there is another board under it.  Certain not good enough if they are directly on top of the frame.  They will flex.