What are the effective ways to use WCFM -Amazon approach

Hi, Everyone.

General questions.
Note, to easily understand my questions and what I wish to archive, is to have Amazon’s approaches in mind as it has many different domains, subdomains, and subfolders, yet have ONE MAJOR DISPLAY STORE to display all the products and services in one place.

1. I am thinking to have a FRONT-PAGE (installation) to e.g. example.com with A-Theme. As a new website, this page will handle introductory to the website, etc, but I wish to have fewer plugins here for fast access. Also, to be on the good side to Google’s new rating requirements, I wish to build this installation with a Gutenberg-oriented theme.

2. Have a MARKETPLACE-PAGE (Woocommerice shop-page) e.g example.com/marketplace with B-Theme, that’s to say two different themes with two different installations. This page (installation) will handle the whole STORES DISPLAY.

My questions are:

1. If I installed WCFM on the FRONT-PAGE (installation) or on a different installation for vendors to sign up, how is it to have vendor’s stores (goods) displayed on the MARKETPLACE-PAGE (shop-page installation)? _If you noticed, the domain Amazon used for vendors registration is different from the front-store domain, yet all the vendor’s goods appeared on the front-store page (domain)._

2. Regarding the above examples or needs, is it okay to have two or three different installations with efforts to use fewer plugins on each installation, and by trying to divide the needed plugin’s usage on each installation yet all to work with each other spontaneously? Also plus the need for two different designs for front and store installations with two different themes, what’s the best option, please?

3. What are the best approach or alternatives as I have started with the multisite approach but noticed that this too, will in the end requires too many plugins in one place, also, nearly all the backup plugins, plus some good plugins are not compatible. However, IF THIS IS STILL THE BEST ALTERNATIVE TO ARCHIVE THE ABOVE NEEDS, I WOULD LIKE TO KNOW? Thank you!

Lastly, on the above needs, what are the best method or suggestions for installing subdomains to complement the above feels, the main domain, Google wise, etc, is it through subdomains (sub.example.com/) or subfolders ?example.com/sub/)?

Thanks for your attention. I’m looking forward to your reply.