Having the upper hand so to speak, it was something that was new for Castiel. With Meg, she always found a way to knock him off balance and remind him that despite being as old as, if not older than she was, he still had very little experience in the things that she had a wealth of knowledge about. All of his experience with dealing with this sort of thing, with emotions and the things that spawned from those, all occurred with her and he couldn't pretend that he didn't hope he was going about things the right way. His time as Emmanuel was something that he remembered, yes, but it wasn't him. He'd been without his memories of who he really was at that time and the things that occurred in that time were not genuinely him. So, this was his first real experience with going beyond the things he learned from the pizza man.
He responded to the deepening of their kiss by testing the waters with his tongue seeking hers out. The movement of her tongue against his bottom lip had been that prompt to him and he was making no move to pull away at this moment in time. There was no hesitation in how he slowly began putting more into their kiss. He retained that gentle and firm nature, but the insistence to deepen that connection and have more with her, it was there. Despite what memories may say about his time as Emmanuel, this was the first time he'd kissed a woman like this and it was rightful that it was Meg, given the feelings he had for her and how implicitly he trusted her with this, with himself.
The light touch of her fingers along his skin, it sent a spark of something through him, something he wasn't quite sure of the name, but knew it was something he liked. Something he wasn't fearful of and a quiet sound got lost in their kiss. The hand that was previously tangled in her hair moved, albeit a moment too quickly and managed to snag just the slightest bit of her hair in the process, but it went unnoticed to him. He'd never really, truly touched her on a more intimate level before and so his hand began to discover that softness of her body in the way that he'd wanted to before, when she'd been wearing very little clothing and nearly in his lap. He was learning her body, so his touch as he began to move about, taking in each curve and line, was soft and steady as his kiss had been just moments prior.