Created a Generic Row to do a lot of regular operation easily

First, I would like to encourage you to take the initiative. However, my advice is not to try reinventing the wheel. Meaning: the row widget already does what you need: it defies the purpose to abstract something that is already there:

Row(
      spacing: 44, /// double here
      children: [],
      mainAxisSize: MainAxisSize.min, /// If you use this, mainAxisAlignement ///will be redundant, because the row will wrap exactly around its children. 
      mainAxisAlignment: MainAxisAlignment.spaceBetween, 
/// there multiple varients of this enum, spaceBetween/ spaceEvently/ ///spaceAround / start /end ...
      crossAxisAlignment: CrossAxisAlignment.center,
/// this controls how your children lay themselves according the crossAxis  //// (for the Row CrossAxis is vertical / for the column CrossAxis is : horizontal )
    );

Now why your approach is bad:

Expanded widget checks the parent constraints regularity and rebuilds the children, whenever building your app to target mobile screens (that have fixed constraints) it will only cause heavy rebuilds at the very start, but if you decide to target other platforms like desktop or web (where you could resize the screen) every time you resize the window the expanded widget will invoke its rebuild, and that could look bad and cause shaky UI.

Plus, your implementation assumes that row uses Expanded widget under the hood, however it doesn't. so please only use Expanded, Flexible, IntrinsicHight ... widgets very wisely because they are heavy in terms of rendering.

One more point: you should understand how the flutter engine works before you do things like these : The flutter render Object has 2 protocols that it implements when laying out the children:

• renderBox protocol: used for fixed positioning: child passes size to its parent => parent passes constraints to its child and the paint begins from the original paint offset: by default it is Offset(0,0) and you can change it if you work directly with Renderobjects. ==> when we use stack, Row, column ... we are implementing this protocol, meaning we should try to pass a child with a fixed size as much as possible because it will make the layout widget's life easier. When we wrap the child with Exapnded, we mean: hey parent, we want you take as much of available space and ignore the child's size because we are greedy, the problem is that the available space can be unlimited, or it can be variable (in this case we will have rebuilds everytime the available space changes)

• render sliver protocol: is implemented in scrollable areas: like listview, pageview .... and customScrollView when you are working with slivers.instead of working with paint offset, it works with scroll offset.