Here is what I have observed about sago palms in Zone 7b. I have one in a pot. It can take a frost ok, but it gets brought inside when there is a danger of a hard freeze. I have to watch for spider mites when inside. A neighbor of mine *had* a large sago palm in his yard, and tried to protect it over winter by covering it with plastic and keeping a flood light underneath. I thought it might work, but it didn't. It turned brown, and never recovered.

I have a huge banana, but it's in a huge pot. Several people in this area keep them in their yard successfully. When the first tiny bit of frost comes the leaves turn brown. What they do is cut the leaves back as much as possible, and mulch the plant DEEEEPLY. They come back in the spring and usually look pretty good by the first of summer.

I don't know a thing about date palms except that I'd like to have one someday.

There seems to be a lot of variation in sagos when it comes to cold hardiness. If I were you I wouldn't take any chances though....whenever its forecasted to go below 25F I'd cover them with a couple layers of frost cloth (Home Depot usually has it) & then add a red heat lamp underneath. I'd do the same for the pygmy date palm too. Forget the christmas lights...they don't generate enough heat to make a difference.

Your basjoos will be fine in the ground. Wait till the first good freeze burns the leaves & then cut the trunks off 5 - 6ft above ground. I've had them begin to push out new growth in early february, so the more trunk you leave the greater head start they'll have heightwise. If we happen to have temps in the low teens forecasted just throw about 6-8 inches of compacted mulch around the trunks and they'll be fine.