I can tell you that in clay soil it is easiest to cut the onions away from the clump with a small sharp spade as they tear easy. The variety I grow dies back in my Louisiana summer and pops back up in the fall. They begin flowering in spring after being in the garden all winter. I still harvest even during flower but they do become blemished and wouldn't be great for market. I also put them anywhere and do nothing to them. I have even thrown them in the grass when I had to many and they rerooted and multiplied on top of the ground. I would imagine you would still need other types to fill the gap if you wanted year round harvest. As far as propagation, I started with six clumps 3 years ago and I have 50 clumps now. I've easily given away 100 clumps and terminally harvested another 100. That's conservative. They multiply like crazy and you can really push them hard by planting single bulbs or you can plant clumps of 3 or 4 for better establishment and earlier production.
How is the taste? Similar to a regular yellow onion?
They are milder than are full size onion south an earthier flavor. There are different varieties that you can choose from though