Looking for Microsoft 365 best practices for a large dynamic company group

Looking for Microsoft 365 best practices for a large dynamic company group

I'm a Microsoft 365 admin trying to figure out the best architecture for a company-wide group (100+ users) and I'm wondering if there's a better approach than what I'm currently doing.

What I need

I want a single company group that can:

• Automatically include users through dynamic membership
• Share SharePoint sites, files, OneDrive content, Teams resources, etc.
• Allow sending company-wide emails
• Allow sending required Outlook meeting invitations (not optional)
• Have moderation/approval for announcements, meeting invites, or posts
• Allow certain trusted users to bypass approval while everyone else requires approval
• Scale as employees are hired/terminated automatically

Current setup

1. Dynamic Distribution List

• Used for company-wide emails and Outlook meeting invites.
• Membership is dynamic using an Exchange recipient filter based on US users.

1. Private Microsoft 365 Group

• Used for SharePoint, file sharing, and collaboration.
• Membership is dynamic through an Entra ID Dynamic Membership Rule.
• I had to use PowerShell to configure some permissions because the portal didn't support everything I needed.

Problems I'm running into

• I now have two separate groups that should always contain the same people.
• The Dynamic Distribution List works well for email/meetings but doesn't provide SharePoint, Teams, or file collaboration.
• The Microsoft 365 Group provides collaboration but doesn't seem to support everything I need for company-wide communication.
• I haven't found a clean way to have approvers/moderators, while allowing a few designated people to post or send meeting invites without requiring approval.
• I also haven't found a good way to make Outlook meeting requests "required" from the sender side other than relying on attendees not changing their RSVP.

My questions

1. Is there a better Microsoft 365 architecture for this?
2. Should I be using a Dynamic Distribution List, a Microsoft 365 Group, a Mail-enabled Security Group, Teams, Viva Engage, or something else?
3. Is there a supported way to have dynamic membership + SharePoint + company email + moderated announcements/meeting invites all in one solution?
4. How do large organizations typically handle company-wide communications while keeping membership automatic?
5. Is maintaining two dynamic groups (one for collaboration and one for email) simply the recommended approach?

I'd love to hear how other Microsoft 365 admins have solved this in production. Thanks!