I would recommend lifting the ply and the tiles then replacing with at least 18mm marine ply and countersunk screws.
H pattern laminate flooring.
Follow these guidelines on solid strip and plank flooring installation.
A screed of feather finish will hide all the screw heads and joints.
A laminate flooring stagger pattern is ideally random with spacing between end joints between 6 and 10 inches depending on the plank width.
H joints are often found on floors laid in a regular pattern these should be avoided for both aesthetical reasons and structural reasons.
Sub floors are typically concrete or cement and develop weaknesses over time.
If you place laminate flooring on a weak or uneven sub floor the new floor will be compromised and eventually buckle damage the laminate locking system creak or create micro gaps in the new floor.
Laying a laminate floor in a regular pattern decreases its ability to contract and expand as a whole unit and instead does so as single laminate boards often causing gaps or even lifting like a hinge.
A random pattern can be hard to achieve when all the planks are the same length but you can do it using offcuts from previous rows to start new rows.
Avoid h joints when installing flooring to give your floor a more professional look.
Trolling many of the diy and home improvement subreddits i have noticed a good percentage of laminate vinyl plank and even some hardwood installations that are installed using h joints rather than staggered joints.
This will leave your new floor ready for any work you undertake from laminate to even a simple sheet vinyl like rhinofloor.
Mar 20 2016 wondering how to install solid hardwood flooring.