Apparently there is a point where Paul Rudd is stuck in the quantum realm for at least 5 years. This is the issue with Avengers 3 and 4 there is 5 or more years where Tony and Captain America had to figure out the Hank Pym technology because both him and his daughter where sent to dust via Thanos snap. It looks like Paul has not aged a day where Tony and Captain America slightly slower have aged. Paul could not come back till Stark could recover him due to the Pym technology outside of the quantum realm.
They then figure out that the quantum realm allows them to do pretty much everything travel through time with the help of an entirely new alien race that can control time travel in an universe that was created from an alien that existed 15,000 years in the future. It also looks like microverse allows Prince Wayfinder to create the Enigma Force alien race who defend space time outside the normal space. Here is where they travel to get the enigma force to help them restore space time to normal but there is the issue. Enigma force created a portal to allow them to travel back in time because it seems that Loki maybe key to getting the stones ahead of Thanos. This is that set photo where Tony, Captain America and Antman are together where everyone else look like themselves from 8 years ago.
I don't know how people can dig this much out of what Paul said but the fact that the quantum realm is tied to it you can guess other comic books that talk about the quantum realm because of the two directors interest in comic books tie in. This may not completely work because when Tony meets Thanos it seems Thanos already knows Tony so it's possible that Thanos already changed the timeline again.
