Unless you plan to go back under the valve covers soon, use sealant and toss the gaskets. Gaskets are fine, but only short term. They will leak. Count on it.

No OEM exhaust gaskets. With new heads, you shouldn't need to use them. Check the manifolds for a true, clear surface. If they are good, no gaskets. If not, have them milled true. If you don't want to do that, use the gaskets or risk it without (my preferred method). The gaskets may leak after some use. Without gaskets, small leaks will seal themselves over time (not a long time), and any leaks will be very minimal. Leaking gaskets are large leaks, especially under load when boost levels rise, and have a tendency to "blow" out. This causes a serious condition which can cause serious collateral damage (and leave you stuck, roadside). Exhaust gaskets, IMO, are a shortcut, and may be a shortcut to a serious crippling failure. No problem using them on a N/A engine, though (little to no exhaust back pressure).