I would be out on Giannis at this point unless you absolutely steal him. He is 31.5 (turns 32 in Dec) and can't stay healthy. Multiple knee, calf, etc injuries. His game is entirely dependent on his athletic ability and with his injuries and his age, that ability is going to to a wall very soon. He doesn't have shooting to bail him out when he loses a step like Durant does.
Sengun+Reed is probably the starting point and they may want Bari+Picks, too.
Then Giannis wants to play with a floor spacing center, which Adams and Capela are not it, so maybe you have to take on Myles Turner as well (30yo). So likely need to add Jabari for salaries to match.
Now you go from a core of Amen, Reed, Jabari, Sengun all in their early 20s to a core of Giannis, Durant, Myles Turner, and Amen - all but Amen in their 30s.
Turner/Adams/Capela
Giannis/DFS
Durant/Tari?
Amen/Okogie?
Fred/Holiday?
A Turner+Giannis for Sengun+Reed+Bari trade adds 14.6M to the Rockets cap, so bringing back Tari and Okogie would be hard, so then you have ridiculous depth problems.
Not my monkey, not my circus, but I would try to move Sengun for someone else, not a super expensive Giannis at the end of his prime. Not sure who all will be available this summer, but ~32yo Giannis + 38yo Durant as your two best players wouldn't give me a lot of confidence in having depth or health to win. Plus that team will suck even worse at shooting.