How many TCP connections will chrome establish when an html page with a css file and a js file is accessed? How many http requests are made?

As the title says.
In addition, is the effect of using ajax to obtain data the same as that of pre-loading the web page? That is, are the established TCP connections and http requests the same?
Would it be very resource consuming if we had to handshake every time? Wouldn't it be better to put all elements on the same page when publishing?