Disable External Sharing Per Library or Subsite

[luvsql]

We need to be able to share anything in OneDrive with external users (using links and not having to specify specific people to share) so we have to enable this on our SharePoint Site Collection, since we cannot have SP with more restrictions that OneDrive.  What if we one say one Subsite in same Site Collection to be allowed and one we don't?  I don't want to have to create all of these as separate Site Collections and want to keep it simple.  

Could I say have one Document Library that cannot be shared with any external users and one that can ie a restriction on the library itself?  Can I have one Site in the same Site Collection that can share externally and one that cannot, without having to put that site in a completely separate site collection?  

[#2]

The sharing options are site collection based, so you must split these to site collections.

However, when you set OneDrive and SharePoint sliders to allow to be shared with "Anyone" SharePoint by default puts all sites not allowed to use "Anyone" by default you have to turn this on in the admin center to allow it for individual Site collections.

[#3]

So I assume the answer is No?  If we have 10 sites (which are SUBsite of one main site), and want a few to allow external and a few to NOT, they have to be completely separate Site Collections?  That gets extremely complicated doesn't it?  I won't be able to simply create a "Subsite" anymore and have inheritance since it's now on another Site Collection. I'll have to instead use pages and lose the old classic look of SP.  

Since OneDrive has a Site Collection called https://MYDOMAIN-my.sharepoint.com and our Sharepoint is https://MYDOMAIN.sharepoint.com, these are already 2 separate site collections, so why wouldn't we be able set SharePoint to NO external sharing and OneDrive to allow it?  If I create a brand new Site Collection and set that to no external, isn't it still on the same tenant and has to be the more permissive as well?

If I create a new Site Collection, it's still under the umbrella of https://MYDOMAIN.sharepoint.com since I cannot change the main URL.  

[#4]

I don’t know th technical reason why the Sharepoint has to be the same or higher permissive but it’s probably something to do with the OneDrive sync client.

Regardless of the setting you can still on a per site collection basis determine what the sharing setting is. This is another example of why Microsoft is pushing us to not use subsites.

You can still have classic pages that are not subsites by changing the experience on the lists and using the classic pages.