mc is roleplaying as other people to practice for his oscar nomination for 2024. he is also hunting strong enemies for fun.

Mc can transform into the people hes eaten up to and including their personality and memories. Sometimes he lets the body go on autopilot while he waits to emerge.

Should have clarified, by "whos who" I meant who or what is MC and is not

He ate him and copied his brain and body to get information

I believe he ate the mayor dude who awarded him, as a transofrmed lizardman (personality him)
then temporarily turned into the mayor (personality mayor) to read his mind
then turned into himself, did monologue, then turned back into mayor (personality him) to address the monster

I'b binging but also skimming so the landshark part was kinda foggy and also not really relevant enough for the plot to explain here

also he CAN read their minds without needing to transform but he has explained that he can sleep as alternate brains to rest his main ones, so he was probably just genuinely resting and thought two birds with one stone kinda shi

he transformed into the personality of the major in order to get more information from him than he would have gained just from absorbing his memories via eating his brain, by living as him for awhile till the major's thoughts drifted to meeting his contact, which gave him the info he wanted to know.

The Sun won't be safe for long, eventually he'll be able to survive in the vacuum of space