ATR schedule is usually 4 on 3 off, because Saturday freight is usually light enough that they fly it on a caravan instead. You have PTO at Empire, not sick time. Also, you get a certain amount of what they call "RX" time every month depending on your run, it usually works out to be about 3 weeks on and 1 off on the ATR.
Caravan is standard usually Monday PM through Saturday AM, but there are a few runs that are Monday PM through Friday AM, and maybe even a few out and backs but these are the odd man out and probably have a guy holding onto them like a death grip.
Yes, you can be hired into the ATR and then go to the caravan, you can also get hired into the caravan then go into the ATR as an FO. If you do the latter you keep your caravan captain pay as an FO I think for 12 or 18 months, then if you haven't upgraded you fall back down to ATR FO pay.