I'd suggest checking manga forums or dedicated Bleach fan sites. They often have detailed breakdowns and recommendations on where to pick up after a specific part. Sometimes, the author or official sources might provide cues as well.
Honestly, I don't know when the TYBW manga starts. But you could search manga databases or ask in manga enthusiast communities to get the details you need.
The Soul Reapers would be very confused at first. They are used to Aizen being a certain way, and Naruto's different personality would be a shock. Ichigo might be curious and see Naruto - Aizen as an ally against the common enemies. Orihime could be one of the first to trust Naruto - Aizen because of his kind - hearted nature that she would sense. And the Espadas would probably be on high alert, not knowing what to expect from this new Aizen.
The TYBW arc's starting chapter isn't a straightforward answer. It could be different based on the manga version and region. I suggest looking at dedicated manga websites or asking fellow manga enthusiasts for the exact chapter.