I used a generic 2004 (20 column, 4 line display) It has the same connector configuration as the 1602 (16 column, 2 line) display that you get with the kit. They plug into the clock kit board in the same way. You do not want a 2004 display with the I2C module attached to it.
Refer to the Operations Manual, Section 2.3 on Page 3.
The Line 1, Line 2, Line 3 and Line 4 configurations determine the clock information which will be displayed on the screen rows (Line 1 = top row). The supplied LCD has 2 display rows but the kit is also compatible with 4-line displays.
So, if you only have a display with 2 lines, you only configure the clock to display information on 2 lines. If you have a display with 4 lines, you configure the clock to display information on 4 lines. Seamless, nothing special.
You configure what information you want displayed and on which line, and if it cycles through various different display configurations. The available data fields to display are shown in Section 2.3 of the Operations Manual on pages 4 and 5.
VE7TK did a really good job of describing what can be done and how to do it, with example images, at -
https://www.qrp-labs.com/images/clockkit/Clock.pdf
73 Fred VK2WS