To help someone who is new to Magento 2 development I'd like to check a couple of things on here if possible regarding Magento 2 (primarily front end) development and how easy it is for new developers to pick up working on existing projects.
The project we have is based on the Ultimo Magento 2 theme which has been extended using a child theme to make some fairly simple changes, maybe approx 100-150 lines of CSS over rides etc. We also have a number of extensions installed (all created by Magento certified developers), like a one page checkout, blog etc, which have also had some customization done to them via the child theme. There are no bespoke extensions created, all the rest of the site configuration is done within the theme and Magento 2 configuration.
When a theme has been extended like this using the Magento 2 best practices is it easy enough for a new developer to work on this site? or would we need to start from scratch?
Yes, a new developer can work with the Ultimo theme for Magento 2.
However, before doing that, that developer should know the basic concepts about front-end development in Magento 2.
I recommend your new developer to read the Magento 2 front-end developer guide: