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.
Xavi has proven his capacity and he has given the title of La Liga and the Spanish Super Cup to Barcelona while the team is down with financial problems. I think it is not appropriate to conclude that Flick is better than Xavi. This season Xavi can also be said to have worked quite well, but he did not get full support because of some things that made internal problems even more tapered. Flick is also a great coach but able to prove that he will be better than Xavi and in my opinion all of that will not be easy.
Indeed, we can't compare Hansi Flick as much better than Xavi. At the start of his debut at Barcelona, Xavi could perhaps be considered not as experienced as Hansi Flick, who already had a lot of experience. However, with these initial conditions, in fact, Xavi was actually able to build Barcelona, which at that time was really on the verge of collapse, because of its financial problems. If Xavi was that bad and not that professional, it would be impossible for Xavi to rebuild Barcelona to win La Liga last season in such critical conditions. Meanwhile, this season, Barcelona finished in 2nd place, not 3rd or 4th or something else. It's just that Barcelona was unable to defend its title this season. because there have been injury cases and several other cases since the start of the season. However, in the end, Xavi was also able to lift Barcelona again from a position that almost slumped again this season. Maybe the results haven't been optimal this season, but it's not that bad..
So now, let's see what Hansi Flick can do with Barcelona. Can he bring Barcelona to win La Liga in his first season as a coach like Xavi did in the past? In the past, Barcelona was also doubtful about winning La Liga because Real Madrid's position was much stronger and more stable last season compared to Barcelona, but Xavi was able to bring Barcelona to win La Liga. So, let's see how Hansi Flick can surpass Xavi this time. The best thing is definitely what Barcelona hopes for, whoever the coach is.
Kroos and Modric are players whose skills will truly be recognized, even though they will not be remembered like Ronaldo, but still most European football fans will know the history these two players have.
They were from the same generation, moreover on Zidan's winning team, if I'm not mistaken. And they became a truly awesome unity at that time. They were the best players in their era, in their respective positions, who supported each other. Modric even got the Ballon d'Or, right? Yes, that's why, indeed, they would still be remembered like the top Real Madrid players before. Even now, I still remember the three mainstay Real Madrid players at that time who supported Ronaldo extraordinarily, the combination of Kross, Modric and Casemiro.

They seemed like truly great bodyguard shining in Real Madrid. Will really miss this composition. Real Madrid's midfield pillar who will be very difficult to replace.
Source: Kroos, Modric, Casemiro