Encryption requires LVM.
The very first thing I would ask is if you really need full disk encryption. Unless that notebook is highly travelled and carries very sensitive information, you probably do not need it and full disk encryption is overkill for the average user.
Not connecting to the internet during installation is fine. Once the installation is complete, you should be able to then connect to the internet and update your drivers.
What is the Integrated Graphics build?
The --class references the actual operating system for the Grub menuitem list.
For example, let's say that you are Triple Booting Mac, Windows and Zorin, you would see the following class options:
--class osx --class sierra --class os
--class windows --class os
--class gnu-linux --class ubuntu --class zorinos
The above are just visual examples; but should convey the meaning.
If it was me, I would not boot with the Nvidia option at all. I would boot with the Integrated Graphics, first. Then set up and configure the Nvidia drivers.