So similar problem here... I've two different vaults, one for private use and one for work. As my phone is basically for private use, I've my MS private account synced in it (autologin and contacts synced too to my MS Live account). The problem, as yours, is that I'm unable to sync my work vault (or any other in OneDrive) because Enpass allways try to connect with my private account to OneDrive and never let me to change my login user (also with autofill disabled). The pretty thing is that with any other webservice, as Dropbox for example, Enpass ask me for user and password, but does not do that with OneDrive.
I bought pro Android app yesterday, I hope anybody can help us. I guess people from Enpass have a look on forums. If not I will contact support and, if I get a solution I will post it here.