Can a sellosity install use a focused funnel with one click upsells using only Stripe, and a regular store using both payment options at the same time, or does that require two separate installations to accomplish?
Your payment options are not actually set in Sellosity, but in WooCommerce, which is the engine. So you can simply stick with Strip and disable PayPal as an option, as in the video below:
From there you can enable the Sellosity Stripe Gateway plugin and then configure it with your keys from Stripe.
Here’s some information directly from WooCommerce: https://docs.woocommerce.com/documentation/plugins/woocommerce/getting-started/sell-products/core-payment-options