I'm not sure how much info they can provide, but I'd check with the UT Ag Extension office. I do know there are professors over at UT that specialize in just about every crop that can be grown around here, and many are extremely knowledgeable. The Extension office people should be able to either provide you with plenty of info or connect you up with someone that can.

Sets ( white ,red ,yellow ) work well but don't store well for a long time . I get mine from the Farmers Co-op , but Ace Hardware in Maryville has them also .
The earlier they are planted the larger the onions will be when the tops fall over and are ready to harvest . Planting the last week of march ( I planted some already because of the warm winter to see what happens ) to the first week of April is what I usually do .
Some can be picked early for green onions .

Onions from seed should be started in January so they'll be large but starting them now is OK but they won't be very large . They do store better than the sets .

Onion plants sold in bundles do well and store well but are exspensive . If money isn't an issue they may be worth the cost .I heard the TexasSweet are best for storing but haven't tried them .

I tried leaving a few onions in the ground last year so they'll make seeds this year to see if I can get them to seed themselves and grow wild .

Growing them in a raised bed with a lot of peat moss mixed in makes it easier for them to grow large . The Farmers co-op sells Esposma Brand organic vegetable fertilizer in 25 lb bags which works well . Adding some bone meal will do them good also .

THanks
My wife picked up some Texas sets. I've got some compost, peat & horse manure that I plan to fill my raised beds with.

With any luck, I'll have the sets in the ground in a few days.

If you're going to try to grow the big sweet onions, could some of you try putting just a few on a really sandy area? IIRC the area where Vidalias are grown is very sandy well draining soil, and I think some folks in west Texas talked about their choosing the sandy areas out there to compete with Vidalias for market share.

here in the midstate garden sets go out in early march.
start seeds in september ,Granex does well