The Modern vs Standard SharePoint site nav disparity

References:

• Jeremy Thake's article
• SharePoint blog on Communication sites
• ShareGate blog on Communication Sites

I have been struggling with this.
If you are an 'Explainer', then  Please explain/comment/opine/discuss on the following navigation disparity. 

A user logs into their office.com tenant using their domain account, and they have a full app launcher experience.

When a user selects the  "SharePoint" app  from the App Launcher tile, they are directed to the "SharePoint Home Screen" which is the new Modern landing page for Modern site creation, with News and sites that you are "Following".

The URL for this landing page is:   /_layouts/15/sharepoint.aspx 

Any sites that you have "Followed" show up here as well as "Featured" sites that an Admin has added (Edit)

There are two types of sites that a user can create from this page using the prominently links:
 The +Create button;
 The Team & Communication site cards

These 2 types of sites are both created using the prefix of "/sites/" or "/teams/" or whatever their SharePoint admin tenant setting "Site Creation"  has been modified to, from inside the SharePoint Admin console.

https://[tenant]-admin.sharepoint.com/_layouts/15/online/TenantSettings.aspx

A disparity in Functionality, URL and Navigation

The new Modern UI sites that are created in the above scenario are terrific, but there is a huge disconnect with the default SharePoint sites. 

Any of the above sites created using the new +Create button:

   1) Do not show in the SharePoint admin console on the right >

   2) Are NOT supported to open and customize in SharePoint Designer.

   3) They do not show automatically in any site navigation, 
        including the standard SharePoint site nav.

   4) Only these Modern sites are surfaced in the Graph and Delve.

The Standard SharePoint sites, at the base tenant [tenant].sharepoint.com have a totally different Site Creation mechanism.

To create a SubSite in here, you choose +New from Site Contents

Standard SharePoint sites have a Fully Customizable UI and can open in SharePoint Designer.

You can program the SharePoint home page as the starting point

See: https://techcommunity.microsoft.com/t5/SharePoint-Blog/Reach-your-audience-via-SharePoint-communication-sites-in-Office/ba-p/70079 

Office 365 Performance Readiness

When transitioning to a cloud first strategy for their organization, many CIOs are reluctant to consider infrastructure upgrades as a preliminary step in migrating from a current On-premises server solution. We have created some guidelines to help you prepare for an increase in internet traffic from your user base.

The benefits of workloads on Office 365 over Hosted applications are clear.

• Best of class collaboration among employees scattered across various locations and geographical areas.
• Better productivity by using multiple devices to access applications.
• Great visibility on compliance reporting.
• Easier setup, little to zero end user maintenance from IT.
• IT resources are freed up from performing server and software upgrades, dealing with licensing from vendors, and general server management.

Your company will experience an fairly significant increase in Internet based traffic. We see an average 40 percent increase in internet traffic across most organizations. This is because all Office 365 traffic is Internet based. You know that users can get to the internet in the office, but your current Internet workloads may not be as heavily used as Office 365 will be. For instance, Your SaleForce.com usage might be representative of a very limited subset of employees. Simply increasing your network capacity is not the panacea that will bring about any Networking Nirvana.

  Routing your desktop users through your network firewalls, proxies and Internet gateways before sending them to Office 365 may just be limiting their experience and could have your end users screaming at you. During the initial migration phases it is the internal networking architecture limitations that’s one of the biggest challenges, especially when users are initially synching their 50GB .ost file!

Readiness To Do List:

• Read Microsoft's network performance guidance
• Upgrade your firewalls
• Increase bandwidth
• Run Office 365 Health, Readiness & Connectivity checks
• Model and test your network capacity or move to an Azure ExpressRoute for Office 365 circuit for a more predictable experience.
• Review your current Firewall software and revise its rules for Office 365.