Storage Solutions?

You could start your droplet off in the entry level size and increase the CPU/RAM as needed. As for your WordPress assets you can use DigitalOcean Spaces. There is a plugin for WordPress that helps with this.

https://www.digitalocean.com/community/tutorials/how-to-store-wordpress-assets-on-digitalocean-spaces

I am working as a web developer in one of the advertising agencies in Dubai. We often use Amazon S3 for the storage issues and it is working for us in a very good way. I recommend the same for you too.

1. Use Amazon S3, mount it to the Droplet and use it as the image file server that Wordpress can use as a gallery. (Is this slow because retrieving each image between servers can have a ping of 180ms+?)

the way that this works is that when files are uploaded they are sent via your server to amazonS3. When the are viewed in the browser, they are served directly from your amazon S3 bucket, through aws CDN. So there is no load on your server, and they are served at full enterprise speed to the end user, wherever they are in the world. something like this: https://www.mhthemes.com/blog/offload-wordpress-images-amazon-s3/

2. Somehow connect Google Drive as the main Wp-content/uploads folder? Possible?

possible, but google drive storage is a different beast to S3, and much more expensive

3 )Somehow connect Dropbox as the main Wp-content/uploads folder? Possible?

maybe, I dont go near dropbox.

4. Use block storage as the mount drive for a $10 droplet and then $10 100gb? Can this still work with a CDN as there are no Sydney servers, which is where we are based. Is block storage and droplet on the same datacentre private networked? How fast is the transfer between the two?

What you are looking for is “DigitalOcean Spaces”. They do exactly what AWS S3 does, for about the same price. Including automatic CDN delivery. Data transfer between the two will be invi