Yes, the performance of Motta as Bologna's head coach this season in the Serie A League will not determine if he will do well at Juventus next season. Juventus is a big club in the Italian Serie A League and more difficult to manage than Bologna because you are expected to win your matches, and if you fail to win silverware as Juventus head coach, you will likely lose your job. Managing Juventus will be difficult for Motta; the pressure to win matches will be high on him, and if he doesn't know the right thing to do, he might use the wrong tactics that give him bad results at Juventus.
Juventus will enter a new era next season with Motta as a coach after last season being last era Allegri at Juventus, Thiago Motta is a young coach and was able to bring Bologna last season into a very strong team and even for the first time Bologna was able to qualify for the Champions League next season, even though Motta is a young coach but I think his ability to coach is certainly worth taking into account by the current senior coach and it is proven by a modest squad but he was able to provide many positive achievements during his time coaching Bologna, when he managed to bring Bologna to the Champions League zone even without a star player, of course he will be able to return Juventus as a challenger to the Scudetto next season.
What you said is true, the pressure of teams like Bologna and Juventus is of course different, but I think Juventus will certainly give full support to Motta to be able to make his job easier later, besides that so far we have known Juventus as a big team that gives the coach full confidence in building the squad so I think Motta will have a lot of time at Juventus later, Because of the fact that Juventus still continues to retain Allegri even though in recent seasons it has failed to lift Juventus performance.