Hi Yafar,
to not let this unaswered: best would be to develop on the Early Access at that point, as the Dev Preview was the „older“ version of the two.
Now there is a Production template and a Development template of Shopware 6, depending on what feature you want to implement, you can decide if you want to use the dev template or the production template (e.g. adding an additional cache system would not make sense in the dev template as it is not using cache at all)
Link to the production template: https://github.com/shopware/production
Link to the development template: https://github.com/shopware/development
Kind regards,
Tim