Please note that the computer certificated can be automatic enrolled through a GPO policy but the user certificate is enrolled after the user logged in once. This require that the AD is reachable with only computer authenication to make (new) user certificate enrollment posible, or just connect once to an open interface.
When you have some computers that are shared between different users this can have some challenge. Thats why i'am personally choose for computer authentication only in most cases.
I look forward to see your test results!