To me this is just the difference in push vs pull.
Send ecash is push to someone
Pay ln invoice is pull from somebody
Send ecash: Users must first choose the ecash option using the toggle switch. Since most users probably want to send payments via Lightning, setting Lightning as the default payment method and then allowing users to select ecash seems like a reasonable trade off. https://m.primal.net/HhQr.mp4
Discussion
This is really good framing.
fyi look at how macadamia has four distinct paths
receive/send being ecash
mint/melt being lightning invoices
I love Macadamia! I'll take a deeper look at their information architecture. My biggest concern with using "mint" as an action to create ecash is how the word can be confused with an ecash mint. I'd also like to see how users react to 4 options. It makes sense to me ,but I worry about less ecash fluent users.
I love the minimal ux, different language use to get used to
i do like that those distinctions are top order and remove the secondary choices you were trying to resolve
perhaps something like:
add
send
receive
pay lightning