This is my first time posting here and was wondering if I was on the right track with my flooring project. My project isn't hardwood, but figured since the question is concerning the underlayment, the answers might be similar.

I live in Southern California and just bought a 1,200 square foot house that was built in 1954. The house has a raised foundation with diagonal plank sub flooring that sits on 2X8 joists that are spaced 16 inches on center.
The plan is to lay 3/4 inch OSB (or 5/8 CDX) over the sub flooring to help level/strengthen the flooring before I install luxury vinyl planks over it. I'm planning on staggering the boards with 1/8 inch pace between them and screwing them down every 6 inches using 3 inch deck screws. The issue is, I keep getting conflicting information on wether or not to use tongue and groove sheets and wether or not to also use glue. Any pros and cons between using nails, ring shank nails, or screws?
If anyone was any insight on this or know any good sites with information or possible videos, could you please let me know?
Thanks in advance
(Update)
I have since decided on not glueing, and that tongue & groove isn't necessary (since it's not subfloor). And normally you would run the boards perpendicular to the subfloor, but since mine consists of diagonal boards, it doesn't seem to matter. So, should I run the boards perpendicular to the direction I plan to run my vinyl planks? Does it matter?

Does vinyl plank require a smooth underlayment? I have never used it. If so I recommend a different underlayment than CDX plywood because of the surface being C grade instead of A grade which is smooth. You would need to fill the knot holes.
You want to lay the underlayment perpendicular to the floor joists and stagger the ends. Plan to smooth the underlayment with a machine like an edger, or electric planer.
The edges need screws every 6 inches and the field can be fastened every 8 inches. Screws will not squeak if you just catch the edge of a joist as a nail would when it slides up and down with traffic and gets loose. Try to hit the center of the joists by marking the joists on the wall and then snapping a chalk line across the room at every joist before you start fastening the sheets.
Once your underlayment is down you can lay the floor any direction you like.
For wood flooring we usually have to flatten the sub-floor which can be done before the underlayment with sanding or planing the high areas and building up low spots with roll roofing. You will have a better quality result if you spend some preparation time before you start with the underlayment.