Not being able to display email and calendar together is a major disadvantage

I have started with em client but I need to see the calendar and email on the same page.
Otherwise I will revert to mailbird, which does that but is not so good to use

The only option in eM Client is the Agenda sidebar, which will give you an easily customized view of selected or all calendars, flagged messages and other folders containing dates like contact’s birthdays or tasks.

If it is not visible, go to Menu > View > Sidebar > Regular sized sidebar. When the sidebar appears click on the Agenda Tab.