Error handling for Cashier Controller methods while building an API

Essentially I have a CheckoutController that handles the functionality for subscribing, unsubscribing, resuming a subscription, and changing a subscription. For example:

public function processCheckout(Request $request)
{
    
    try {
        $plan = Plan::findOrFail($request->billing_plan_id);
        $user = $user = auth()->user();
        
        //If user has no subscriptions subscribe them to new plan
        if($user->subscriptions->count() === 0){
            $user->newSubscription($plan->name, $plan->stripe_plan_id)->create($request->payment_method['id']);

            return response([], 201);
        }
    } catch (\Exception $e) {
        return response([], 500);
    }
}

What I don't understand is what type of errors I should output for the frontend to pick up if something goes wrong. Right now for all of my Checkout methods I just out put a 500 error, and on the front end I catch that error by outputting a message: "An error occurred. Please try again."

submitPaymentForm(paymentMethod){
        this.$http({
            method: 'POST',
            url: 'api/checkout',
            data: {
                billing_plan_id: this.planId,
                payment_method: paymentMethod
            }
        }).then(function (response) {
            this.$store.dispatch('getUser')
        }.bind(this))
        .catch(error => {
                this.serverErrorMessage = "An error occurred. Please try again.";
                console.log('submit payment'+error);
        });
    },
},

Now, I do understand that Stripe implements its own errors on the frontend, but I'm not sure what to do with my backend. I was hoping someone could help me out with this.

Here's my full gist of the functionality