For the first few weeks, Juventus, AC Milan, AS Roma and some other contestants will probably be competing closely with Napoli and Inter Milan in the race for the Scudetto. Napoli seems to be stronger among the other contestants because Conte is staying, besides they are also actively adding strength by recruiting experienced players like De Bruyne. However, let's see first how other Serie A contestants complete their plans in the transfer market, as you said, it can be a reference to assess how ready they are all to face the challenges in the next season. Inter Milan don't seem to be as strong as last season, as they have parted ways with Simone Inzaghi.
To be honest, I no longer have high hopes for Inter Milan for next season. because I think Inter Milan can be very strong in the last few seasons also because they have a talented coach like Inzaghi. So when Inter Milan loses Inzaghi, I think Inter Milan's fate is still uncertain whether it will improve or vice versa.
Meanwhile, Napoli and AC Milan are the ones that I might expect to compete closely in the race for the title in the upcoming season in Serie A. Napoli may have a busy schedule because they will also be playing in the UCL. Meanwhile, AC Milan can focus only on the domestic league. Which in my opinion will bring benefits to AC Milan.