Welcome, my name is XXXXX XXXXX I will do my best to help you with your issue
Don't use luan. It is notorious for delamination failures. There are other plywood options that are made specifically for underlayment for vinyl and they come with a delamination warranty. You should use 1/4" minimum. I don't know what's available in your area so specing a specific product probably won't be much help
Thank you - Do you think 1/4" will prevent buckling?
It won't buckle if you nail it off properly and it doesn't get soaked. Proper nailing is 6 to 8" apart in the field and 3 to 4" along the edge. IntegraPLY is what we use and I see it's also available at Menards which is in an entirely different part of the country
The Integra PLY even have X's printed on the sheet where you should nail (ring shank nails or screws)
Great - sounds like a trip to Menards is in order.