Installing on a computer with data etc on it - does it wipe the drive, or will it be like an upgrade install?

Assuming MacMini 2011/2012 iwth SSD running High Sierra. If I upgrade to Monterery or Ventura using OCLP - will all the data/users etc be there, or does the process wipe the drive? It's not totally clear to me from reading the docs. (I know I should back up before doing it).

Any common gotcha's or risks one should know about?

Thanks!