I added Pro Site to my multi site website: everything works

Hi

I added Pro Site to my multi site website:

everything works fine I guess but here are some challenges I have:

1- When a user signs up and choose the Theme nothing happens and it loads the original wordpress page

2- Can I use a different login plugin instead of core wordpress? if yes which one you recommend

Where can I access the shortcodes for after login, what I want to create is a page with links to account setup and ability to include all the features that agent can use.

Thanks
ELi