Need help with forum structure and Mongoose

TL;DR: Need help with the structure of my forum(how to model it with Mongoose).

Hello world, I’m coding a forum using express and pug for my portfolio(looking for a job), the forum is already working in the cloud but I’m storing the info in memory. I just have days with Mongoose and I have never created a forum, I would like to have some recommendation on how to model the forum. I already have a structure made with typescript interfaces but everything is stored in RAM memory:

My board structure looks like this:

1 Boards(index)
2 Board(group of categories)
3 Category(group of threads)
4 Thread(group of comments)
5 Comment

In the process of initializing(I kinda still need this with Mongodb) the forum I have a function which creates all routes and pass all the info to the render method, then I display everything using for loops inside the pug file.

My big question is: should I create a big nested model? or link everything with many models? I’m kinda confused right now mainly because my knowledge of Mongoose is weak. If you have a better idea please let me know!.

Question 2: Is there any info on how this forum as created?

Many thanks!!