is it possible to have the gallery, attachments and downloads get uploaded to like a google drive space or the cloud somewhere?

You can certainly you Amazon S3 or another S3 storage. However, all your storage needs to use that.

in other words, once you implement it, that's where it has to be, correct?

do any instructions for this exist, is so, where may I find them?

As in that you can only have one storage configuration on v5. You can change it but you can't have gallery on S3 and forum attachments on your local host.

Here are instructions for Amazon S3, they are likely outdated but the same premise is there:

https://invisioncommunity.com/4guides/advanced-options/server-management/configuring-amazon-s3-r230/