The way I see it, Cloud didn't fully sort out his feelings for Tifa until the lifestream sequence. From what's shown then, he at least subconsciously remembers that he has feelings for Tifa. The feelings are still there of course, but they don't really take their relationship beyond friendship until later. I figure the Highwind scene can be interpreted as being when it happens, or maybe they talked about it post-game. Before that, Cloud's issues and Tifa's reluctance to confront him about them meant they had to deal with that before they could really deal with how they felt about each-other.
While Cloud obviously cares deeply for Aerith for reasons beyond possible influence from Zack, I always viewed their relationship as platonic, which doesn't make it any less meaningful. Aerith is a lot like Zack, in that they both seem to be the kind of people who can befriend just about anyone willing to reciprocate and brighten things up just by being there. Whether or not Zack being Aerith's boyfriend influenced Cloud's interactions with her is debatable and Cloud obviously doesn't remember Zack so there's only a small chance he was reminded of him on a subconscious level. Either way, Aerith still starts off as a stranger to him when they first meet and gradually get to know each-other over the course of the game prior to her death.
I don't really think Cloud's all that different before and after he sorts through his memories. By that point, he already dropped most of what I associated with his false persona, leaving just the identity issues and Sephiroth's ability to control him.
