Managed to install Sitecore 9.1, highly recommend to use step-by-step installation guide here- https://buoctrenmay.com/2018/11/29/sitecore-xp-9-1-step-by-step-install-guide-on-your-machine/

Sitecore admin password is no longer b and is generated after the installation is complete.

scadmin

So, remember to note down the auto generated password or reset password once logged in.

Enjoy Sitecore installation!!!