checkout - logic error? and "Proceed to Checkout" button stays

Hi,

The situation you're describing is normal.
The order is created the moment you click on the "finish" button of the checkout. After that, you can change whatever you want on the products in the order, it won't reflect in the order.
As an analogy to the real world, the finish button is the moment the last product goes through the cashier, before you give your credit card.
At that point, even if the remaining stock of products in the shop is removed from the shelves, or if the price of the products in the shelves change, it won't reflect on your bill.

Also, on a technical point of view, when you click on finish, HikaShop creates the order and send the data of the order to Stripe so that Stripe can display the payment page. If you change the order in the mean time, then the payment will still be processed by Stripe with the old amount and it won't match what's in the order.

The only solution to that is to have the pay occur just before the order is created. That is possible with some payment gateways like PayPal Pro, Authorize.net in AIM mode, etc. In these cases, the credit card form is actually displayed during the checkout, and when you click on finish, HikaShop pre generate the order, asks for the payment to be processed with the credit card information it got from the customer, and just after that create the order in the database.
But the Stripe API we're using doesn't support that.

Regarding the cart module displaying the proceed to checkout button on the checkout, usually, what you do is that you remove the cart module from the checkout and use instead the "cart" block of the "checkout workflow", or you configure another cart module without the proceed to checkout button display option turned on so that it display on the checkout instead of the other cart module.

Regarding the locking of plugins options when you edit them in Joomla, HikaShop is not involved and you should have the same behavior regardless of the plugin you're editing.