If you have video and audio attachments, then it may become very large. Even if you only allow images, it may become very large because of the count of them. There is no any issue here. The addon allows you to manage file formats and max file size. You can disable vido uploading or set maximum file size 1MB even less. In any case, it's up to you.

I found that the main folder with the biggest files was my wpforo -> attachments folder.

https://prnt.sc/1b29ms7

Just wanted to know a few things.

1. Is this folder basically the pictures/videos/pdfs stored in the advanced attachments plugin add-on?

2. If this is the case, is there a way to make sure that the files uploaded to the website aren't so big in size? 

3. Or, if I was to stop using this plugin, is there a way of making sure the previous posts that used this add-on still display the picture/video that was in the post normally?

4. Is the main alternative to this plugin the WpForo Embeds add-on?

Any insight would be appreciated, thanks!