Creating a permission set that grants field service users access to the Order object is a granular and secure way to provide the necessary data visibility. This allows for precise control over which users have access to order data without impacting other profiles or requiring additional licenses. Salesforce's permission set documentation provides guidelines on how to grant specific access rights to users, ensuring they have the information needed to perform their job functions effectively.

This way, you can preserve the historical data of your sales transactions related to the deactivated products without deleting them from Salesforce. You can also avoid syncing issues between your ERP and Salesforce by keeping the product status consistent1.
Deactivating a product in Salesforce means that it cannot be added to new opportunities or quotes, but it remains visible on existing ones1. You can also deactivate all related prices for that product at the same time by enabling a setting in Product Settings1. To mark an opportunity or quote as inactive, you can use a custom field or a workflow rule that changes its status based on certain criteria3.
https://help.salesforce.com/s/articleView?id=customize_product.htm&language=en_US&type=0

Option B is a solution that can help AC Computers avoid hitting governor limits when processing large orders because asynchronous Apex can run in a separate thread and use higher limits than synchronous Apex1. For example, asynchronous Apex can process up to 50 million records per transaction, while synchronous Apex can only process up to 50 thousand records per transaction2. By moving some of their automation processes to asynchronous Apex, AC Computers can reduce the load on their Salesforce environment and improve performance.
A Solution Architect should evaluate moving automation to asynchronous Apex to resolve the issue of hitting governor limits when trying to create and activate orders in Salesforce. By moving the automation to asynchronous Apex, the automation processes can be run in a separate thread and will not affect the transaction limit for the current thread. This will prevent governor limits from being hit and ensure that the order creation and activation processes can be completed successfully.