If he unlocked SSB/PSSB form during Boo arc? This SSB form is from the manga version where it's kinda 10x of SSjin or depends on how you interpret Whis explanation.
If we apply 10x SSJ, in Buu Arc, it'd make him 2x-2.5x stronger than his SSJ3 self. He would surpass SSJ3 Gotenks but still be weaker
than Ultimate Gohan in my books.
If it's stacked on top of the SSG ritual, he solos Z.
If it's only added to his previous forms with the gap between Boo Arc SS3 and this SSB form being the same as between that of his forms from the U6 Arc and onwards, he'd be lucky to beat SSJ Gotenks (post) with SSB and certainly wouldn't be touching SS3 Gotenks with PSSB.