Hello,
Characters are tied to platform accounts. If you have a set of characters on Playstation, these characters are permanently tied to that account, and cannot be removed or transferred. Cross save lets you access these characters on other platforms, so that you can play with them on multiple platforms.
I believe that the characters you want to use are tied to your playstation account. Therefore, you cannot link a different playstation account without losing your characters.
[quote]When you set up Cross Save on your Bungie account and choose the character set you want to use across your connected accounts, that character set will become your active Cross Save and set of characters. That means that if you log in on any platform you have connected (Xbox, PlayStation, Microsoft Store, Steam or Stadia), those characters will be there. Your other characters on those platforms will become dormant - you won't lose them, but you won't be able to access them either. [/quote]
More information on this is available in the[url=https://help.bungie.net/hc/en-us/articles/360049498031-Destiny-2-Cross-Save-Guide] Cross Save Guide.[/url] I would recommend reading it thoroughly so that you can understand how this process works.