If we talk about tactics, of course it will be different and the difference will probably seem quite large. I think Hansi Flick is much more reliable than Xavi and everything will change as long as no problems come. Maybe Barcelona should be able to strengthen their players' physical strength so that they don't get injured as often.
I am very sure that if most of Barcelona's players can avoid injury then they will be much calmer in navigating the competition next season and at least they should not be outside the top four in Hansi Flick's debut as coach. However, if we talk about competing with Real Madrid, it will still be quite far away and it will be difficult for Barcelona to match it.
It's too soon to say if Flick can perform better than Xavi or not because we can't forget Flick had a bad performance in Germany and some people believe this coach couldn't be a good option for a team like Barcelona because Barcelona can have much better coaches instead of Flick in their team.
Regardless of that, Flick made his first decision in Barcelona, and as this first decision, he wanted to expect the contract of their captain Sergi Roberto.
When Xavi was working there, Sergi Roberto was even close to leaving Barcelona but since his contract was about to end, Flick asked the team to extend his contract for a longer time.
Coming to conclusion yet no performance too show already is too soon for judgement, let watch closely to the changes he'll bring to the club