you shouldnt clone autos, but u can, although it will stress the clone and it can turn hermie, its not advised but it is possible if u really really really want to. Just get more seeds, or get regular auto plants n get ur own seeds.
in terms of yeild, with the right genetics and set up, i think the most anyones got off an auto is around 360 grams. yes. they can produce very high yeilds if u pick the right variety and always grow it under the specific strains optimum environmental conditions. although, your more likely looking at around 3 ounces for a single plant if you consider yourself a knowledgable grower with a 400 hps or roundabouts light output and good container/soil/nutes/ventilation etc
There are so many varieties to choose from. Some take 6 weeks, some up to 9, and some haze varieties can take 90+ days. Most varieties should start flowering after 2-3 weeks on 20/4 light cycle, although some phenotypes and/or strains are unstable and may not be auto at all. best to shop around and check reviews. there is an auto thread on rollitup. an ultra lemon haze auto i came across on a seedbank recommends a 12/12 light cycle and 90+ days whereas there are others that can fully flower on a 24/0 or 20/4 light cycle in 60+ days.
good luck, its a really interesting and exciting world. but like missnu said above ^ they can be a great addition to a regular photo strains grow, because they can be harvested while a normal photo strain has still got a way to go, so u have smoke before ur main harvest. some auto strains have very high resin production, like i said shop around nn check out grow journals and reviews !