If I was going on a road trip and had some meat I smoked then vac sealed and froze in portions, how long could I carry it in an ice chest and still be safe to eat? Brisket, pork butt, or chicken would be the meats to choose from.

I would give it the standard left over rules of once thawed of 4-5 days after, After that I would probably be tired of eating that much bbq.

Good cooler, frozen packaged meals. Layered 5-10# of dry ice will keep frozen on our river trips for 10 days

Yep, we've left Wyoming with 2 160 qt Coolers full of elk. Have cardboard layer protecting meat from dry ice then tape cooler closed. 2 day drive home, 2-3 days before processing and meat is still frozen.

Just don't have the dry ice up in the vehicle with you.

It's still good as long as it passes the sniff test

As,long as it's on ice, I would say a week or more. It'll take a few days to thaw. Once it thaws, that's when your clock will start. Cooked meat will last much longer than raw.

Dry ice on top, or on the bottom of cooler? It’s been a long time since I used any.

Either way works fine, dry ice is minus 100 degrees and will cool anywhere in the box. The real key is how you are using the foods, and how many times you'll access the cooler every day. With the items loosely stacked where you can get some air flow is better. I like to put one piece in the middle and one on top. Every time you open it, the top piece will thaw a little quicker. If you figure out the order you're gonna use the meals and layer them in there like that, you only need to open it for about 10-15 seconds each morning, and get your stuff out to thaw. We bring back 8 1/2 gal of Blue Bell in a Yeti each time we come home from AZ that way.

Dry ice puts off CO2. It can cause oxygen depletion. Put the ice chests in the trunk or bed of the truck. Don't put it up front with you in the cabin of the vehicle.