There's so much to say about this. Here are a few starter points:

Leyland cypresses are pest magnets, but 'Green Giant' arborvitaes are seldom bothered by bagworms so that shouldn't be a concern for using them. However, all choices will have some pest/disease issues, so choosing a variety of plants (and avoiding a monoculture) is probably the best idea.

Especially if you choose to use only one type of plant, loosing one can be a problem visually. Imagine a row of trees with one or two missing. By using a more naturalized planting scheme and choosing a variety of plants, you can greatly reduce the impact when one fails, as well as reducing the chances of a total wipeout (which monocultures encourage).

All of the choices you've mentioned can get pretty big. Is space/mature height an issue? That's one thing you'll want to consider when choosing plants and when deciding how to plant them.

Not all fast growing trees are quick to dies and weak-wooded, but that is the general trend. On average, the quick growers tend to be quick diers.

Especially if you choose quick growers (like 'Green Giant' arborvitaes, for instance), start with smaller plants. A one to three gallon 'Green Giant' can outgrow an originally-larger specimen in just a few years. The smaller ones are also less expensive, much easier to plant, and better able to adapt properly to the planting site.

There are many, many similar posts to yours in the Trees and Conifer Forums. You can find many similar recommendations to the ones I've made, as well as specific plant recommendations (for various similar situation) by searching those two forums for similar threads. You might also get more specific recommendations by posting in the Trees Forum and including LOTS of specific details about your goal/plans/site.

hmmm, i do like the green giant arbivitae, but i have a few leylend cypress and bagworms totally destroyed them, thats why im leary of the green giants, but you say the bagworms wont bother the green giants?

I've seen hundreds of Leylands and many many Green Giants in landscapes and borders. I have quite a few Green Giants in my own yard. I've seen almost no Leylands without bagworms. I've never seen a bagworm on a Green Giant that I can remember.

Before you start sticking in a bunch of Green Giants though, take a look at a few during winter months.