Ah, I understand now. Previously you said "inside the Wiki page menu", not "Settings". That confused me.
You can see the content templates dropdown selector when creating new page at the Properties tab. If you want them present more visibly to new page creators, you can disable the tabs interface maybe? You can also copy the link leading to Content Teplates in the Settings menu to your own menu if you want to provide it more visibly.
No, there is no templates dropdown selector. When a user clicks on Wiki page/Create a new page, only a text input field comes up, asking for the name of the new page. After that is entered, a dropdown list comes up asking which language to assign.
Content templates are ONLY visible in Settings/Content templates, which opens the admin page for templates. There is no dropdown list. At least not on my Installation of 18.3. Since I do not assume that this is a bug no one besides me has noticed, I suspect there is config setting that blocks such a dropdownlist.
On my old Altair Wiki (that still runs), there was indeed a dropdown list, right on the page creation page.