I received two job offers, the first is on h2b visa, the lawyer is waiting for the approval from USCIS and the second one is on j1 visa. The first will start in mid Nov and the second one in early Jan. I was wondering since the time frame will be very close, is it possible for me to change my visa status from h2b to J1 or from h2b visa to tourist visa without having to leave US ?

I was also wondering whether it's common for US employers to change their employees visa status from h2b visa to h1b?

Thank you