He was okay ish at Lazio if I'm not mistaken and killing it this year with Inter. Think he has some more way to go for proving himself. Same goes for the other Serie A coaches.
Inzaghi is an interesting case. Keep in mind that the main lure for many people on here is quite similar to what drew them toward ETH a few years back: a glamorous CL campaign. What could possibly go wrong, huh?
Anyway, there are pros and cons when it comes to Inzaghi. For once, it has been interesting to see him develop his preferred 352: From a risky high/mid-press with both wingbacks positioned high on the pitch at Lazio with lightning quick transitions that led to both scoring and conceding lots of goals and distinguished him among his (more defensive-minded) peers, to the more controlled, but still more fluid than anything Conte had implemented version of the same formation at Inter which failed to land the Serie A title, and finally, to the more structured yet still flexible (within the frame of positional play) and, in the end, quite pragmatic edition that's going to win him his very first league title.
It is interesting in the sense that he will immediately find himself under enormous pressure at OT, and this is how he has reacted historically when the stakes were high. And the stakes were high because it is expected of him to win the Serie A. With Juventus in disarray and with Inter having the best squad in the country, one could argue that it took him too long to deliver. The big bonus is that he has been constantly adding qualities to his tactics. Layer upon layer, you can see shades of Pep, Bielsa or even Wilder in his ideas. After all, Inter's biggest strength under him is that they seem comfortable with any role: Underdog or superior side, possession or counter-attacks, open games vs more tight affairs etc., they can be competitive either way. The way he wants his midfielders to play (deeper than usual to see more of the ball and dictate the tempo) can be a remedy for our lack of options in receiving the ball on the half-turn in tight spaces between the lines, but it works because the centre-halves offer options in the positional rotations. Options like the ones ETH is being called a madman to try and create. So, good luck with that, if Simone lands the United gig.