I can't say anything about typical. My Rex are pyschos, even though they are all handled after birth, and spend more time with me than with there dams. I have culled half of my herd due to temperament, and have had my hand gorged twice by two different rabbits, one a buck and one a doe (two different lines completely). I have heard similar, and from judges. Because they are not as easy to find, I think this creates a serious temperament issue in the breed, we keep things we have no business because they are hard to replace.
As far as grow out, I'm not the best person to ask, grow has always been my chief complaint with Rex, because they are supposed to be a commercial breed. For the past two years, I only had 2 buns reach 5lbs before 5 mos, over a total of 200 kits. Finally I am getting 5lbs at 12 weeks, but only one or two out of the litter, and I'm culling all others. I hear the same complain on the Rex breeder pages. They have fallen out of favor with meat breeders because of NZ, so a lot of the people raising them are for show, and aren't as greatly concerned with fast growth rate. Slower growth sometimes equals better fur quality, and that's more important.
I do get huge litters,10-12. Litter size does matter ,but the litter of 9 now, is about 3 lbs at 8 weeks. Another litter of 4, is barely 1.5lbs at 6 weeks. I plan to cull that entire litter and the dam. Mola kindled 7/21, and her kits are almost the same size as the 6 weeks olds.
Rex on the West Coast seem to grow faster than the East coast. Maybe more breeders over there stayed true to the meat breeding aspects of Rex.
If you decide, find someone who breeds for meat, and is mainly concerned about meat. Although I am trying to improve the size of my Rex, they are quickly losing favor as my primary show breed, too hard to get quality stock. I gave up on them as meat breeders, that's why I got the Silver Fox, and decided on French Angora instead of English.
In order of feed conversion, Silver Fox, Rex, Angora.