Odoo.sh or Odoo Online
The most consequential choice in setup: it decides how quantities sync and which screen you get.
What the difference is
Odoo Online (SaaS) is Odoo hosted on odoo.com, where you cannot install custom addons.
Odoo.sh or self-hosted is Odoo you control fully, where you can install addons.
How to tell which you have
If your Odoo URL ends in .odoo.com and you have never installed a third-party addon on it, you are almost certainly on Odoo Online. If you manage the server yourself or use Odoo.sh, choose the other option.
This changes your sidebar
You get exactly one of the two quantity screens depending on this choice: Products Quantities on Odoo.sh, or Products Quantities (Online) on Odoo Online.
What it means in practice
On Odoo.sh, quantities sync through the Tecfy addon installed inside Odoo.
On Odoo Online no addon can be installed, so the connector builds what it needs inside Odoo itself: a model, some fields, and two scheduled jobs. See the Product Quantities section.
Sidebar not updated yet?
The sidebar reads your hosting type, Odoo version and product-push settings from the session, loaded once when you sign in. After changing any of them, sign out and back in so the menu matches your new settings.
The default is Odoo.sh
If you choose nothing, your account is treated as Odoo.sh. If you are on Odoo Online, set this explicitly — otherwise you will be looking at a quantity screen that cannot work for you.