I want to create soft animation between transitions in simply UI:

        
scrollToPoint is not animatable. Only animatable properties like bounds and position in NSAnimatablePropertyContainer are animated. You don't need to do anything with CALayer: remove the wantsLayer and CALayer stuff. Then with following code it is animated.
- (void)scrollToXPosition:(float)xCoord {
    [NSAnimationContext beginGrouping];
    [[NSAnimationContext currentContext] setDuration:5.0];
    NSClipView* clipView = [_scrollView contentView];
    NSPoint newOrigin = [clipView bounds].origin;
    newOrigin.x = xCoord;
    [[clipView animator] setBoundsOrigin:newOrigin];
    [_scrollView reflectScrolledClipView: [_scrollView contentView]]; // may not bee necessary
    [NSAnimationContext endGrouping];
}