My wpforo -> attachments folder is very large

Hi, I need to free up space / buy new space for my hosting and website so I can create staging copies.

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!