Only way to do that is probably CBSubs Options. You can then have multiple ways to pay on a single plan. So for example you could have a plan that bills every 2 months, or every 6 months, or once per year.

Set your plan to allow recurring payments under the Pricing tab and that's all there is to it. If your plan allows single payments and recurring payments you'll have 2 payment buttons during checkout to select single or recurring. The only thing you'd need to be sure is configured at Stripe is Webhooks.

That error is kind of a catch-all. It basically means the response body encountered invalid characters. This typically means your web host is blocking Stripe or something in Joomla (e.g. some sort of security extension) is blocking Stripe. If your server has a firewall be sure to whitelist Stripe IP addresses and domains below.

stripe.com/docs/ips

Recommend contacting your host as they should be able to check security and access logs.