That could be viewed as fraud at the time of entry under both scenarios. I recommend that you speak with an immigration to come up with a workable plan. Note that if your spouse applies for his or her green card visa (known as an immigrant visa) at a U.S. Consulate, he or she can visit you on a tourist visa for extended periods of time while waiting for the interview at the U.S. Consulate.
Thanks for the info. Tricky situation because we have a kid who has dual citizenship, and we are not in the US, but want to move back.
Your best bet is to plan a year or so ahead and get sponsorship in the queue so the spouse can enter with a green card. Timelines are about 8-14 months.
But as PRoberts said, a non-citizen spouse can't enter on a tourist visa with the intention to change status. A spouse can visit, but then change their mind while in the US.
But CBP is well aware of people trying to shortcut the process this way, so it can be very challenging convincing CBP your non-citizen spouse intends to leave. But it can be done showing a job, property or other elements that would require someone to go back.