Advice on moving pictures to a host for CDN

Hi Wappler nation. Just asking a bunch of Qs - please answer what you can. Thanks!

NOTE: Our App, while accessible worldwide, is mainly used in the Southeast United States. It will be heavily hit during a one-week period in October. Continued use may occur, but nothing like during the event where we want to provide speedy access to pictures. Thats why I’m thinking of a CDN. We will have between 2500-3500 images that will be repeatedly viewed.

Currently, our wordpress site allows users to upload car images (pics) as part of a form entry.
Those pics are stored on my host (1and1) in the normal Wordpress “uploads” structure.
Shared sites like this are crammed on servers for lots of websites, so i’m at the mercy of their bandwidth and cpu. Thats normal.
But I’d like to explore moving my pics into a more formal CDN using Fastly or Imgix, for example.
(main reason is for dynamic sizing so I’m not managing multiple thumbnails)

From what I read, Fastly/IMGix sits “between” my raw pics and the enduser.

1. Does this mean that my “raw” pic has been copied (duplicated) from 1and1 and resides on Fastly? If so, then I SHOULD NOT be worried that the server might be under heavy load (ie. slow) as that won’t affect content delivery to an enduser, right? So pics could stay on 1and1.

2. Since I’m now using Digital Ocean for my live Wappler site, should I move all my pics to DO?
   If I’m going to use Imgix, do I even need to do this?

3. What is this service on DO called? I see I can add more block storage to increase my droplet storage. But where/how do I copy a bunch of pictures to DO? I have storage containers in Azure but don’t see a similar thing in DO. (again, I may not need to do this based on the CDN)

4. I’ve always heard that AWS was more expensive than most other things. Yet people here talk about S3. Whats the benefit of my pics being in an S3 bucket?