Looks like a typo in the XML. Fixing for next build. You can quickfix with the below.
IN: components/com_comprofiler/plugin/user/plug_cbpaidsubscriptions/processors/stripe/edit.gateway.oem.xml
ON: Line 38
FROM:
Code:
<param name="id" type="private" class="cbpaidGatewayAccountstripeprooem" method="renderUrl" value="notifyurl" key="id" label="URL to set into {PSP} admin area in API - Webhooks - "URL to be called"" default="First fill-in parameters above, then "Apply" this new gateway settings: Then this URL %s will be computed and displayed." description="This is the "URL to be called" to paste into {PSP} admin area." />
TO:
Code:
<param name="id" type="private" class="cbpaidGatewayAccountstripeoem" method="renderUrl" value="notifyurl" key="id" label="URL to set into {PSP} admin area in API - Webhooks - "URL to be called"" default="First fill-in parameters above, then "Apply" this new gateway settings: Then this URL %s will be computed and displayed." description="This is the "URL to be called" to paste into {PSP} admin area." />
Webhooks are not necessary though so it's not mandatory to set them up. Single payments initialize and pay immediately. Without webhooks you won't be able to refund from Stripe and have it cancel the subscription or if a payment is put on hold it won't pay once it comes out of pending state (shouldn't happen as far as I'm aware).
As for it taking 30 seconds I observed the same during my tests, but I've no idea why. The slow down is coming from the HTTP request to Stripe. Nothing I can really do about that unfortunately. I believe the slow down should only affect test purchases while live should be a little faster. Maybe contact Stripe regarding this to see if it's normal.