The way I have always done it in the past:
Create virtual account with voicemail. (199)
Ring group 200 destination if no answer -> voicemail-> 199 (unavailable)
On the phone, instead of adding account two. Change the voicemail button dial string from *97 to *98199
No need for a second account, will update the MWI on the phone and opens the mailbox when you press the button.
Your problems:
I don’t understand what you mean destination for voicemail… You select voicemail first, then a second field will pop up and let you select from the enabled voicemail boxes.
the default behavior of a virtual extension with voicemail enabled is to go straight to voicemail. But don’t destination calls to extension 199, send the destination to the voicemail of 199.
By setting voicemail to *98199 on account 1 you will get MWI.