It isn't just Inle lake that is interesting but the surrounding towns and their temples (don't have the names off hand but 2 days would be necessary). I think an overnight in Inle lake is too short to see these. Spent 4 nights there in January and that was even a little short if one wanted to see more.

I'd consider flying from Bagan to Heho if the flight exists on the day. Too much time spent trekking to and from RGN otherwise.