Ok there is a lot to cover here

1, Many, maybe most fruit trees sold in a typical big box store garden center will not be climate appropriate for where you live.

2, Most of the fruit trees found in garden centers, etc. are older varieties because they are cheaper to grow as the growers don't have to pay royalties on them, like they would for newer (perhaps better), patented varieties. Plant patents are valid for about 20 years, and can be issued to people that breed a new /improved variety of plant, such as a better tasting, or higher yield peach tree.

3, There is more to selecting a fruit tree than picking something you think would taste good, at a minimum you need to pick something that will grow in your growing zone, and something that is in the right chill hour range for your location. Too few chill hours and it will wake up too early in the spring and possibly loose its buds to a late season freeze, too many chill hours, and it may delay bud break in the spring, produce few, stunted fruit, etc. Google chill hours, and look at one of the chill hour calculators for your area, the University of Mississippi recently released a chill hour counting web app

4, There is more to climate appropriate then the above, In the case of pears you have European pears, as well as Asian Pears, if choosing a European pear for central Mississippi you will want a southern variety, also one that is fireblight resistant. You need 2 different varieties of pear trees to cross pollinate to maximize fruiting. Remember just because the garden center sells it does not mean it will live in your region long term. They make their money off of people planting the wrong things then having it die in 2-3 years, then buying something else.

5, If you don't want to do lots of research consider varieties of fruit trees that were developed in the region, there are a number of thornless blackberries developed at the University of Arkansas that should grow welll in your location, though some may work better than others ( most of these have Indian names, Osage, Ouachita, Natchez, etc.) There have also been a number of varieties of peaches developed by LSU over the years, though peaches are more chill hour specific, they also require an active spray program for pests in our region, the same goes for plums (Aurburn University has released several good region appropriate plums over the years). As to pears there are not many newer southern region European pears out there, so this is one place where newer is not always better. Having said that often the vast majority of the pears you find in a typical garden center are more appropriate for growing in northern states. Google is your friend, look up the information on the name tag before buying.

6, The good news, is given your location on the 7b/8a line there is a lot of stuff that should work ok for you.

You need 2 different pears, NOT the same.

I'm not familiar with many varieties. I love Bartlett and Bosc, don't like Seckel. I don't think you can really go wrong, but I'm sure others will provide better advice than I can.

If you pick them up from Lowe's or a big chain store, they will be semidwarf, which can take up to ~8 years to fruit. If you want fruit faster, you'll have to find a local tree nursery who can get you a dwarf tree on special dwarfing rootstock, then you can get fruit in just 2-3 years, but then the tree will never grow much beyond 10 feet tall.

Hope you find what you like. Good luck.

Fruit trees need to be adapted for your particular climate. For that reason alone, I would avoid the box stores - they purchase in bulk for an entire multi-state region and often offer stuff that is just not suitable. Local independent nurseries do a better job and your feed store may fit into that category. But you should really check first with your local extension office - they will always know the best selections for your area and can also recommend those that are known to be most disease resistant, so you reduce the need to spray continuously.

Many fruits are self incompatible, meaning they will not fertilize themselves and produce fruit. To do that, you need two different types for cross pollination. Even supposedly self-fertile fruit trees will produce bigger and more reliable cropping if cross pollinated.

MS Extension Service offices

http://extension.msstate.edu/sites/default/files/publications/publications/p0966_1.pdf

I'm also in MS and have used this publication a couple times to aid in narrowing the varieties.

That does seem to be a good guide, I have read similar guides put out by other university in the region, and unlike most this one seems to have actually been updated in the last 30 years, not just reprinted with updated photos and graphics. Though at least on some of the fruits listed, I would guess its last real update was made 10 or so years ago, as it is missing some of the newer Arkansas thornless blackberries, etc.

You can find good stuff at box stores at better prices than most other places. For example, I just moved to GA and Lowes/HD have Kieffer Pear as the only pear for sale, these are bulletproof. They carry rabbiteye bb's, again bulletproof. Elberta peach is the only peach they are carrying and that is a good choice too. Always double check with your phone on the internet. For example, even though they have loads of potted Rabbiteye BB's they have another section with bareroot BB's that contains Northern Highbush types, not good for the south. Also double check the tag, don't look at the big box store retail tag but the sticker from the wholesaler on the pot, that will be most accurate.

I agree the big box store nurseries can provide the best bang for your buck, though one does have to be more aware of what you are buying. This requires doing research, on average many of the things being sold there will not be climate appropriate, or they will be less than optimal varieties. Sure Elberta is a good peach for places with ideal climates for peaches, but it is also an 18th century variety that can be propagated and sold by anyone, no royalties required. Though in the 148 years since it was introduced, people have bred many improved varieties, some are more heat tolerant, others are provide fruit with longer shelf life, or more resistance to various diseases. So sure Elberta is still a good valid choice in prime peach growing parts of Georgia, it may be a bit less than ideal in hotter, more humid regions of Mississippi, where one of the varieties developed by LSU or the University of Florida in the last 20-40 years may be a better choice.

Big box stores also tend to do no selection and culling or poor quality trees, ones with poor grafts, or other deformities, though I am not saying most private nurseries are much better on this point. Just another buyer be ware concern, along with lax labeling with in store tags, just the other day I was at a big box store garden center and found a citrus hang tag on what was obviously an olive tree.

When I'm at the store, I constantly look up the varieties on my phone to make sure I get what will work. You definitely need to know your chill hours so you get something compatible.

Lowes by me is pretty good. HD sometimes too. Look up how to prune those trees, and look for the best form at the store.

Make sure you plan your install site also to meet sun req'ts, etc.

I ordered blackberries online, because I wanted the UArk varieties.

Just research a little, go shop, and have fun.