Drupal 8.x

I am trying to customize the user registration page of the website (also the login page). My main complaint is the default user registration page looking awful (yes, it is functional, but does not fit with the rest of the theme and the way it displays the logo at the top - it does not work for my square logo) on my site - for most other websites this is perfectly fine.

I have Googles for instructions on how to do this, but everything I got stopped at Drupal 7.

I want:

Hi,

We currently have 2 sites built with Drupal that share the same codebase but the sites are built separately. They are for two separate brands that do essentially the same thing so the sites are very similar including the same content copied and pasted as they have a separate database per brand. We are now looking to add another 10 brands (which was never the plan when the site was built in Drupal) so exploring better ways of working.

Goals:

Build the page once and publish across all sites

I made a D8 website with Composer on my development server. Now I'd like to upload it to the server of my client but it has no Composer. 

Will I be in trouble if I just copy it as is?

composer.json
composer.lock
vendor
web

to the domain root?

I hope this is the right place for this. I am trying to subtheme bootstrap4. I have changed all the necessary files to my theme name and have my new theme installed and set as default. The site renders without any styling whatsoever. After reading the README again I discovered I needed to update an import in the scss/style.scss file. I have tried every known possible combination of my site relative paths but I cannot get this to work. Can anyone shed some light on what I'm doing wrong?

According to the readme...

Hello all,

I am looking to add eCommerce functionality to my site so that I can sell unique keys to customers which is currently running Drupal 8.

The main two commerce solutions I see are Drupal Commerce 2 and Ubercart. Though out of the box both Drupal Commerce and Ubercart modules for selling keys are only for Drupal 7 and depreciated. 

Was just wondering if anyone has done something like this using Drupal 8 with either of these eCommerce solutions or if there is an alternative option for accomplishing this.

Any help is greatly appreciated.