iCloud Shared Library setup with large photo library on iPhone and MacBook Pro

MY GOAL: 

Activate shared library for myself and eventually with wife and kids.

CURRENT STATE:

Large Library – over 100K photos.

Iphone 15 with iCloud photos ON.

MBP M4Max with iCloud photos OFF.

-For my MBP Photo Library, I've always imported photos via plugging phone in with wire and downloading/importing (hence why iCloud photos is off on MBP).

-My Phone has about 6K photos on it.  Many of them are on the MBP in various albums on photos library, but not all of them.

WHAT ARE BEST NEXT STEPS?

-Before doing anything on MBP… should I set my Phone photos to Optimize iPhone Storage? (right now the phone has download/keep originals on).

-On MBP should I activate iCloud photos and wait a day or two before turning on iCloud Shared Library? (to give time for iCloud to update 80-100K pics).

QUESTIONS?

What will happen with the current photos on my phone?? 

Where will my phone photos go on my MBP after iCloud photos and shared library is turned on? 

      For example, if they are already in an album on MBP will they not be duplicated?

Other helpful tips and tricks please!?!?

NOTE:

I plan to keep the originals on my MBP and backup copies of Photos Library manually to an external SSD on a regular basis. 

[Re-Titled by Moderator]