Levels are shit for Ragna.
It's what makes 2C a worse move overall since it's nerf from level 4 to level 3 from CS1 to CS2. It's +1 either way, but worse as a move in blockstrings and such because of it.
Levels indicate how much blockstun and hitstun a move have. Hitstop can affect what it feels like, and spacing and pushback can affect it's relative safety and all, but the reality is those numbers are never actually changed.
If a move is level 4, and you rapid it immediately as the opponent blocks it, than you are +18. Simple as that.
Now if the moves pushes you back significantly upon successful block, even if you rapid it, it's not gonna feel like you can do much. Ragna's 2D is a perfect example of that, the pushback on that makes rapid cancelling it in blockstrings a questionable thing to do to attempt to restart pressure. It's level 5, so you're +20 on RC, but you're gonna be spending a good amount of those plus frames covering the distance to get back in your opponents face, plus the start-up of whatever you decide to throw out whenever you get close. I mean, he has 5B and 5C so it's not TOO big of an issue, but it's still not the best idea, save the meter for something else, etc.
Disclaimer: I'm pretty sure this is how things work. I could be wrong, it's been a while since I read the system mechanics and all that.