Something that I really like about the first few openings is that they emphasize the duality between Usagi Tsukino and Sailor Moon. Usagi and Sailor Moon are often shown as two separate figures, never touching. This represents how, in her early days as a Senshi, Usagi really didn’t identify herself as the warrior of love and justice, Sailor Moon. She was just plain old Usagi, a klutzy crybaby with a loving family and bad grades. It wasn’t until she grew into her role as a Senshi did she start identifying herself as Usagi, a klutzy crybaby with a loving family and bad grades who just so happens to fight against evil as the beautiful sailor-suited warrior, Sailor Moon.
The dual imagery isn’t present during the second opening of the first season; by the time the second opening replaces the first, Usagi is secure in her friendship and camaraderie with Ami, Rei, and Mako (and later Minako); with her teammates on her side, she doesn’t feel overwhelmed or alone anymore, and she becomes confident in her role as Sailor Moon.
The first opening of the R season, however, throws some heavy dual imagery at us. This is because, all throughout the Doom Tree Arc, Usagi is heavily conflicted about her role as Sailor Moon after regaining her lost memories of the first season. On one hand, she knows that being Sailor Moon is extremely important and she has her teammates with her. On the other hand, she got a taste of what it was like to be a normal girl again, a girl whose only major worry was failing an upcoming test and being scolded by her mom. Several episodes reveal that she can no longer use Moon Tiara Action or any other magical attacks because her resolve isn’t strong enough.
However, by the time Chibiusa falls into the plot (literally), Usagi is once again secure in her identity, and the dual imagery doesn’t pop up again.