This was the solution to the problem, I also had to make a start state from a RobotState Moveit msg (different from Niryo One RobotState msg: easiest solution is to import it with a different name) and now the robot is moving great. Pre-processing is super efficient for what I wanted: for anybody who wants this specific solution here is a little comparison of what you can get from this method : On a 10 tries gcode test containing 172 points
-Python API via n.movepose() : 7 errors, average elapsed time when success 161.375sec
-Compute_cartesian_path() : 0 errors, average calculation time: 1.151sec, average execution time:14.77sec
Compute cartesian path is a really good solution to have a smooth trajectory, it has great results but you will not be able to move the tool as n.movepose() do.