@Daojoan I use DT for some of my research PDF archives. Its very, very good at searching collections and within documents. You can create search workspaces, add smart rules for multiple things, and create notes but I dont do that as would rather have notes in markdown separately. A drawback of DT is its a proprietary format but you can search in their databases without using DT itself if you need to.

@Daojoan Starting is very simple: Create a database, add PDFs.

How you continue depends on your use case.

I encourage you to read the handbook.

https://www.takecontrolbooks.com/devonthink-4/

@Daojoan Drop it and go #Obsidian.
In all seriousness, I was and early Devonthink user and it was my go to app for about 15 years. Then Obsidian came along. My big drawback with Devonthink is that the creation and editing tools are cumbersome and access to my files outside of DT was frustrating.
Start with one database and add things as you like to see how it works for you. It is a fabulous app.

@Daojoan I’d start small—make a couple of databases, drop in a few notes or PDFs, and get used to tagging and smart groups. Once you get the hang of it, you’ll see how powerful it really is.