I cant change the new tab to my preferred home tab layout and want to bypass the default Mozilla private browsing layout

Nothing is imposed. The whole browser is driven by layout markup that's accessible to everyone to modify as they wish (if they assume the responsibility for maintaining that going forwards of course).

You might wanna ask around in https://www.reddit.com/r/FirefoxCSS/ for details, and write up your preferred layout to your heart's liking (and it's possible somebody has done that same before you, so you can just follow their steps…)

Bonjour

Is it these questions?

Set an alternative home page when opening a new tab https://support.mozilla.org/en-US/questions/1480324

Customize private browsing page https://support.mozilla.org/en-US/questions/1588497