Integration with CB shouldn't be required. As long as the template is Bootstrap 4 it can style CB in addition to it self. This assumes the template developer didn't, for reasons unknown to me some developers keep doing this, tamper with the core Bootstrap styles and break their behavior. If the template is Bootstrap 4 then you should be able to turn CBs Bootstrap off in CB > Configuration > Integrations.

An alternative is to use CB Template Changer and its built in Template Builder feature. This lets you restyle CBs template so its colors can better match your Joomla template.

--- nice login screen (example 1: slide panel on the left side)

Our login module is using Joomla CSS classes and structure so any template should be able to style it already. As for the position that's just an "offcanvas" module position that many templates have and just needs to have a login module placed in it.

--- login avatar (example 2: right bottom image)

That's just the login module. All you need is a module position then display the login module in it.

--- pms alert (example 2: red number)

New PMS icon is built into CBs login module. Enable it then use some CSS to reposition it. You don't need a template specific integration for this.

We don't have such a list. We don't develop templates at this time either. I can only comment regarding your tick boxes for integration with CB as I've done above. Any Bootstrap 4 template that fits your style should be sufficient.