There are almost an infinite number of different kinds of plywood, from cheap to eye watering expensive. In general if buying from a reputable supplier price is an excellent guide. cheap is almost always bad, expensive is always better. But do you actually want a teak plywood that has been made with all veneers also of teak and the top veneers that are actually millimetres thick rather than microns thin. If you want it it’s available (I actually have some) but you will be paying very much more than anything else, I paid about 6 times more than an equal sized good quality board and about 10 times more than a cheap one, and I live in the country where it is produced.
Good quality plywood will not delaminate, the glue is normally a heat activated one. Cheap plywood will delaminate because they had to cut corners to make it cheap, these will include, less glue, less pressure in the curing press, less time in the press, less heat in the press etc.
to answer your question first is the “marine” plywood expensive? If yes has he got any that has been cut, I ask because if there are voids or overlaps you will almost never see them in a full sheet.
if the answer to both is yes it’s probably an OK choice.
if the answer to the first is yes but no to the second then ask about voids and overlaps, if he’s a reputable dealer he will tell you and replace a sheet if it’s not the quality he claims and not good enough for you.
FWIW I would add a second strip, probably about 100mm wide round the edges as IMO it looks better
