I am affraid this is not a sollution for my problem. I don't need to make mograph text but to somehow extrude splines and round their corners. I made something that looks like this, but rounding with subdivision surface or bevel does not work. Screen 1 is the result of extruding (and it is quite ok), second is the result of the first one subdivision surface and third is the first but changed into editable and with beveled corners. None of them is perfect and this is the problem.