What's your question? Ask

Many people do divide and transplant hosta but it isn't necessary. Since you want to propagate them, here is how:

https://www.gardeningknowhow.com/ornamental/foliage/hosta/dividing-hosta-plants.htm

I'm not sure they are tough enough to be a roadside barrier. You may end up with a lot of tattered leaves.

Dwarf mongo grass comes in many varieties. I'm also a fan of Shasta daisies. They're low maintenance and stay in a nice circular clump, like a hosta. If you cut off the blooms as soon as they start to fade, you may get a second flowering out of them. Lilies are another option.

I've never seen a white hosta at all. 'White Feather' hosta emerges white in the spring, but during the season turns green or with green variegation. It is only 6 to 10 inches tall.

This can be done, safely, at any time. Here is a collection of articles that will help:

https://www.gardeningknowhow.com/ornamental/foliage/hosta

You can dig them up and put them in plastic nursery pots so you can move them. Add some potting soil to the container below and above the plant. Water when they dry out. You can keep them in the garage till you are ready to plant. I would wait till next spring to plant them in your new yard.

Since they have been there that long, go ahead and wait till fall to transplant. You can trim some of the leaves when you transplant. If you are experiencing high temps, you can erect a shade cloth over your hostas to protect them till fall.

https://www.gardeningknowhow.com/ornamental/foliage/hosta/transplanting-hostas.htm

https://www.gardeningknowhow.com/garden-how-to/info/shade-cover-tips.htm