So, you can certainly fly in manual mode if you want - but I'm curious why you want to.
In general, quads are usually in some sort of self leveling mode. When a moderate gust of wind cones by, they correct themselves back to level. When you stop a turn, they return to level. If the quad is a bit off balance, it works to keep itself level anyways....etc...
When I had used manual mode, I would use a switch to flip between Attitude (stabilized) flight mode and manual. I wouldn't trust myself to fly manual without a way to quickly flip back to a stabilized flight mode.
I think you'll find a flight mode that does what you want without going full manual. For example, I wanted my quad to flip - something I couldn't do in Attitude flight mode. But if I changed it to Acro+ flight mode, when I push the sticks near their extreams, the quad no longer tries to self level and does flips! Returning sticks back to center makes the quad self level again...if you think I could do 3 flips in one second and then manually recover before crashing.........well sometimes even the FC can't do that
There are a variety of flight modes you can set in librapilot. This link should help pick one.
https://librepilot.atlassian.net/wiki/display/LPDOC/Input+ConfigurationThere are also a variety of settings to change how 'snappy' or 'smooth' the quad flies. This link should help
https://librepilot.atlassian.net/wiki/display/LPDOC/Stabilization+Configuration