If you get J1 waivered, then you can re-enter USA without subjecting two year issue. You can stay or leave from USA.
You don't need wait for H1b before applying for GC. You can file NIW even you have J1 visa. Do not waste time.
You don't need wait for H1b before applying for GC. You can file NIW even you have J1 visa. Do not waste time.