Here's my answer to the disappeared posting requesting info. took two days of leaving and coming back to it, so I gots to post it. Possible fishing for ai sourcing, or just an absolute innocent newbie, or lazy. Or both.                                               If in earnest: here goes....

Well, right about now the forum appears not highly populated with real hands on, 'invested',  posters so I don't know that there might be response enough to serve your ends. Let it be said there is a wealth of experience in the archives of this and the forerunning predecessor forum of the Home Orchard Society (r.i.p.), and I'm pretty sure the topic is very well covered.

So, a couple of things to consider about varieties. What's offered may not be what you want/like. Learning to graft would help with that, particularly if you want something you can not readily find at the grocery.

Placement of grafts on the tree; tree form. Will you manage an espalier, or are you looking for a tree bush form. I'd assume either on a dwarfing rootstock. You may want the 'pedigree' (name variation) of the root so you can look up the attributes. The difference between one garden department "semi-dwarf" and another or other various dwarfing rootstocks, can have substantial differences, not only in size. Disease resistance, need for support or self supporting come to mind.

The vigor of the fruit varieties will play as well. Vigorous types located on upper tiers of an espalier form will shade out less vigorous below if not managed with that knowledge. Tree Bush form, you might well pay attention to planting with the more vigorous limb on the north side.

Oh, and pollination requirements. probably only comes into play if you're  planning to graft/build a tree. Commercial nursery grafters usually have that timing figured out. The apples need to blossom in overlapping times. 'A' is early, b, c, and d follow. B will pollinate those apples that blossom in the a, b, and c bloom time. And so on.  

Karen T spoke to a point; if grafting your own for espalier, you might develop the first tier and let it establish for a year anyway, to get a head start before grafting for the next upper tier. And again if your design plans want to incorporate a third level.  As I've traveled around for my work (unrelated) I've seen lots of espalier with the upper tiers really shading out the lower due to vigor or spacing or lack of maintenance or combinations. 

Might be something there for your consideration. If you've got the passion and the time required, git goin'.