Odoo's documentation states that Odoo Online is incompatible with custom modules and with modules from the Odoo Apps Store. Studio customisations are fine on Online, but any custom Python module means Odoo.sh or on-premise.

If you start on Online

• Moving later is possible: download a backup from the database manager and import it into Odoo.sh or restore it on your own server.
• If your Online database is on an intermediary version, upgrade to the next major version first, because those versions are not supported on Odoo.sh or on-premise.
• Odoo Online upgrades are mandatory on a schedule, and Odoo upgrades the database automatically if you take no action by the due date.

If you go straight to Odoo.sh

• You need an Enterprise subscription that includes Odoo.sh and a GitHub repository for your modules.
• Production is backed up automatically every day, and staging branches give you neutralised copies of production to test changes safely.
• Upgrades are required after the support period ends, and your custom modules must be made compatible with the new version before the database can be upgraded.

If you self-host

• You can stay on a version as long as you like, but you own security, HTTPS, PostgreSQL administration and backups of both the database and the filestore.

Our advice for your case: if the commission module and courier integration are likely within your first year, start on Odoo.sh to avoid a migration in the middle of your roll-out. If they are uncertain, check first whether Studio and standard features cover them; if they do, Odoo Online is the simplest start.

Whichever route you choose, test the plan in a duplicate or staging database and confirm the details against Odoo's current documentation and your subscription terms.