Hi this is a late reply but I thought I give you my opinion.

Regarding database I tend to recommend developers to keep their own db at the beginning of the projects for a couple of weeks. I do that because the fact that we usually change the definitions of pages and blocks a lot in the beginning of a project. If a developer starts to work with "my" things we might end up the need of manual work to either install a new db or rollback properties on contenttypes. The reason for this is that once an object has been used by an editor we might not be able to change things in code anymore.

After a couple of weeks when things are more up to speed I sugest working togheter on the same database. But still I prefer having a local db :)

We use the shared database and assets folder from day one :)

Usually two developers don't work on the same page type / block / view at the same time.
When they do, then every developer creates a new page in edit mode for testing -> JohnTest, MikeTest, etc.

We also have a definition of done by which we have to test everything locally and on the test server before we resolve an issue in Jira.
Having a shared database saves us a lot of time.