Summary
After looking like he was close to falling out of the league around 2016, McGee revived his career by playing a legitimate role on championship teams in Golden State and Los Angeles. He even started the entire regular season for the Lakers in '19-'20. However, his minutes fell drastically in the playoffs, as he was taken out of the starting lineup and sometimes didn't even get minutes.

McGee played well for the Suns in '21-'22, even stepping up and starting a number of games when Deandre Ayton was injured. He has always been a good finisher at the rim due to his size and athleticism, and his numbers bounced back from a down year in '20'-21. He has a big catch radius and good hands, allowing him to catch tough lobs and finish in traffic. On defense, he chases blocks a little too much, but can be a legitimate deterrent at the rim.

However, he really struggled to make an impact for the Mavericks in '22-'23. He averaged the fewest minutes per game of his career, and he was eventually pulled from the rotation and waived that season.

McGee will be 36 years old as a free agent in 2024. While he has fairly recently shown he can be a solid backup on a really good team, didn't make much of an impact in Sacramento in '23-'24, and his NBA career could be in jeopardy.
 
Cap Considerations
McGee will be an unrestricted free agent with a $2.1 million cap hold and Non-Bird Rights. This means that the highest starting salary the Kings could offer him using the Non-Bird Exception is $4 million. This should be enough to retain McGee, since he settled for the minimum of $3.2 million to come to Sacramento. Alternatively, the Kings could use their Mid-Level Exception or Bi-Annual Exception (if available) to re-sign McGee if he demands more than $4 million. 

Other teams will have multiple ways to sign McGee as even teams without cap space could possibly use any of the Non-Taxpayer MLE, Room MLE, Taxpayer MLE, or Bi-Annual Exception to sign him. It's also likely that McGee only gets minimum offers, and may not even get fully-guaranteed offers.