I'm pretty much with Jeff. I don;t cook quite that high (225-250) but I'm sure that 275 will work as well and a little faster. You will learn how your smoker works. It is entirely possible that a 275 reading on Jeff's smoker could be the same as a 250 reading on mine. The last batch I did took about 6 hours.
I don't wrap but others do and get great results. Wrapped ribs will be a little more 'fall off the bone' and if you like them that way, then wrap.
I'm sure they'll be great!