If I didn't know better I'd say your photos showing plywood floor were my own---that's very similar to my own method.
Here's some images of my floor, no particular order: https://imgur.com/a/nNnMq5b
I did and will use 3/4" BC interior grade, sanded one side. When picking out your sheet goods pick pieces without any voids etc in the "good" side--makes applying your final floor covering massively easier and a better finished look too.
I did mine in nothing but 96" lengths---there's no practical benefit to special ordering 10' sheets. In fact three 4x8 sheets will do the entire floor from just behind the front seat bases to the very back. Any seams or joints you'd want to add for ease of handling the material can be easily crafted so you're not handling anything larger than 4x4 pieces.
On my next floor install (soon to begin) I'll run two 8' sheets from the back to halfway between the wheel wells and gas filler bump. They will be cut to fit the body just under the flange, the template being the original floor mat but I'll add about 1/4" to the pattern and trim as needed.
I'll split each sheet somewhere near the middle of the van so they meet near the middle where they'll span a wide space between the floor ribs. IIRC that space is close to 2" wide. The gap is about 1/2" deep so I'll cut 1 1/2" rabbits in the plywood sheets along their length and across the front edges too. Length-wise I'll run strips the full length and screw through the top sheets into the strips between the ribs--this is a super strong joint in this use.
At the leading edge of the longer pieces I'll use the same 1/2" strips but more as "fingers" running under the cross-wise seams, long enough for maybe 2 screws on each side of the seam.
It might not be easily seen but I did eliminate the factory side step as that's very convenient for my van's use. Because I run DIY running boards entry to the interior isn't an issue, the space resulting from covering the side step used for miscellaneous storage. This might not be desirable for RV/camper use.
In the last two photos of that link I show how I capture the floor under the flange I mention.
If the floor is cut for a snug fit there would be little to no real movement of the plywood against the Raptor lining to cause any issues. You won't gain anything with pads ect between the plywood and metal floor ribs I dare say the Raptor liner is strong enough to not be bothered by even a little movement---its mostly used in pick up truck beds anyway so it has to be able to resist quite a bit of wear and tear.