1) Some varieties are self-fertile, but even self-fertile ones are more productive if there is another compatible variety nearby. So yes, planting in pairs is a good plan. There are some which are "triploid" and are complicated to pollinate e.g. Bramley - best avoid them until you have 3-4 other apple trees at which point they are often worth considering.

2) Enterprise and Liberty apples are foolproof. Many of the McIntosh style varieties are also very reliable. However an important part of low-maintenance fruit trees is the right rootstock, if you have the space then a semi-vigorous cold-hardy rootstock or an interstem rootstock is a good choice, so that you have a free-standing tree that will tolerate periods when you forget to water it etc!

Not so sure about pears and peaches.

Thanks OP. I only have a quarter acre lot, all pie-shaped backyard, so I'm trying to maximize the use of space leaving room for raised bed gardens. I figure that I can place a total of 5-6 trees back there. I probably will look for semi-dwarf or smaller varieties.

I have no direct experience in your region, but have come to respect the recommendations from DWN for my location. They have recommendations that may work well for your locale as well:
DWN Planting Recommendations in USDA Plant Hardiness Zones 5 - 9"

If you follow the directions for Backyard Orchard Culture, you will be able to plant more trees and have ripe fruit over a longer period of time.

Welcome Coach... great to see another Idahoan here (I also live near Boise). If you want to plant this year, it would be best to do it soon as the heat is on the way...

If you are close to the city or suburbs, you will likely be fine with a single apple tree. There are crab apples EVERYWHERE and the pollen is compatible. The blossoms are just beginning to open right now. Are there any in your area? If you are unsure, you can plant two (must be different varieties which bloom at the same time).

I planted two European pear trees this spring (Ubileen and Highland). I believe that the flowering pears will also pollinate the fruit trees, but I'm not sure on that one. We have a lot of ornamental pears in the area, which are almost at petal fall now. Again, if you plant two, get different varieties. I picked my two based on their ripening times, one in early August, the other in October (trying to spread out the fruit over several months).

Most all peaches are self fertile, so you'll only need one.

Many on here may disagree, but I'd pick varieties based on taste and ripening time more so than disease resistance. The disease pressure here is very low because of the rain-free bone dry summers, so fruit trees are fairly easy to grow. You'll have to fight a few insects and birds, but I don't know of any insect or bird resistant varieties. We generally have low insect pressure as well because of the cold winter and lack of humidity. Feel free to send me email if you have specific questions (like nursery rec's, etc).

University of Idaho has great information about growing fruit in Idaho. They break the state into zones and they evaluate fruit by taste as well as hardiness.

I've used their information for choosing plants for Central Oregon and found it to be quite useful.

Thanks, I found their website.

Here is a link that might be useful: Univ of Idaho

If you have neighbors they may have fruit trees that can pollinate. Check for self-fertile varieties. Also, you can get multiple pomme/stone fruits grafted onto the same tree. That way you don't need to worry about cross fertilization from another tree.