Hello,

My vote is for Custom development.

To not start from scratch:

There is a wordpress plugin that sends new woocommerce customers and orders to odoo:

https://wordpress.org/plugins/notify-odoo/

I can modify it to send other wordpress data if you need.

Also there is a plugin that sends form data from wordpress to odoo:

https://wordpress.org/plugins/wp-odoo-form-integrator/

It still works with Ninja Forms 3.7.0 with minor adjustment:

https://wordpress.org/support/topic/update-for-php-7-4-and-ninja-forms-3-7-0/

Stanislav