Converting to Drupal

I wish to upload a MySQl database data with members from an entirely custom (Non CMS) website to bring in members and their data into matching fields in a drupal 8.x.8 website.

Obviously the fields would need to be renamed if I were simply to do a find and replace within a text editor of the insert statements in a *.sql file!

The point is, I could simply copy and paste corresponding field names for Username, email, old non-encrypted password, First name, last name, job title etc fields into those of the new drupal site.

I suppose the questions are:

Hello everyone!
Using DEV I installed Drupal 8 and installed an old drupal 6 site locally.
I would like to migrate from D6 to D8 using Drush, but when I run the command

drush migrate-upgrade --legacy-db-url=mysql://db:db@127.0.0.1:32772/db --legacy-root=http://mysite.ddev.site --configure-only 

I get this error:

Hello,

I have two Drupal 8 sites installed with composer.

One is old and installed with drupal-composer/drupal-project which has been deprecated.

The new one is a clean install using drupal/recommended-project

Can I install the same Modules without doing it manually?

Can I migrate the content to the new site?

Thank you!

I tried to comment on an issue about this, but my comment was not visible after sending with "Save". Maybe this could be because I registered recently, but I could not see any feedback about whether the comment was saved or queued for review, or rejected. So I guess my first, or additional, question is how to comment on an issue in the correct way, and how to know what happened with the comment text I posted?

Hello everybody,

We try to migrate all of our Drupal WebSites from an on-premis infrastructure to Azure WebApp, all of the settings, deployment script are functional but during the test period we experienced a lot of latency mainly on backend (for example sometime it takes more than 30sec to be logged on the backend).

All the pages on the backend are really slow to be loaded.

We use an Azure for MariaDB instance with the same setting as on-prem.

I was thinking about converting from a Joomla 3.9 component to a Drupal 8 module. Maybe a custom template too. Of course Joomla does not have 'content types' but uses database tables directly.

So, a question that popped up is: when should I use 'content types' and when should one use the database within Drupal 8 more directly? Is it considered 'working against Drupal' if one uses database tables instead of content types?

What advantages and disadvantages are there to both methods?