Will shipping thresholds created in shopify work for upcoming subscription orders?
As Bold Subscriptions integrates with the Shopify checkout, the shipping rates you set up in Shopify are also applicable to your customer’s subscriptions by default — unless you have set up fixed shipping rates using Bold Subscriptions.
If you have questions about how specific shipping configurations from Shopify work with your subscription orders, it's best to reach out to Shopify.
Generally speaking, Shopify uses the least expensive shipping rate for recurring orders.