Ductwork For A Popup Vent

We're planning for a new cooktop with popup ventilation. We'll have to start with 3-1/4x10 duct and run it down into the basement. Then a 90 elbow and a transitional piece to 8" round. From there it goes to the blower unit (600CFM) then to the outside where we install a wall cap.

Do we need heavier gauge pipe than what's sold at big box stores?

Should we tape the joints? I have some that's reinforced and some plain. Or should we use duct seal?

Are the transition piece and cap big box parts or will need to start searching elsewhere? I've found the transition online for about $30 but have yet to find the cap. Any ideas where to look if HD doesn't carry them?

Thank you,
Julie

One other question, for the wall cap we want it with a damper that actually works, in other words, one that closes and stays closed when the blower is off and doesn't flap in the wind or allow critters access. Any suggestions on a brand?