Is this cage tutorial a good one?

This one here:

https://www.youtube.com/watch?v=YAjfrdOJEM0

I'm not much of a carpenter, so I'm not sure the design is a good one. Or whether it's safe for a beardie.

No.

It might be in certain places, but generally no.

A cage like that would be appropriate as an outdoor enclosure, but not indoor. Assuming that you use air condition that cage won't be able to maintain high enough temps for your dragon.

You need a fully enclosed cage. Either a fish tank style cage, or a fully enclosed wooden cage with glass front (there are a variety of materials actually, but generally it's type of wood a glass or plexiglass).

Just take a look though the threads in this forum and the enclosure forum and you'll see plenty of good examples.

Maybe in some cases. I’ve had this idea for a long time and I will share it with you, and it’s pretty simple: Get free wood pallets on Craigslist (prepare them; sand/cut/tame nails out) and create a terrarium shape, leaving the top and front open. Put two pieces of glass in the front (make sure you put places where they can slide)
make sure they overlap one another about halfway. For the top, get some window screen (Lowe’s, Ace, Home Depot) and use industrial glue to have a screen top. For a more detailed version, contact me on my off topic forum called questions. Place your substrate inside, then your food and water dishes and then rock/wood structures and thermometer/probe/heat gun. Place your lights on top, turn them on, and put your beardie in. I hope this helped