For Q1 I would allocate 3 to 4 hours to install Moodle. It all depends on where you are starting from.
Cloud space is often a just a chunk of disk space so first you sp an operating system. Installing Linux or even a LAMP stack is quick but even so you need to add users, set the the domaiin, add https, check and configure PHP including all the extensions required by Moodle, secure the database, run the Moodle install, then set up cron and backups of the database. And that is assuming you are not setting up a mail server.
Q2. Never underestimate the ability to screw things up. Don't skip time on snapshots and back up
Q3. I add users using bulk load
Q4. Always auto installed plugins and it worked for me. Check for version compatibility, test before loading to production and keep it simple.
Maybe someone has an up to date stack ready to drop Moodle on top. I find I have to start from scratch.