By default, the product list module control offers different selection choice of page size that affects the number of items displayed on the page at a time (e.g. 10, 20, 50). If you want to change the default selection, you can simply create a custom display template for the Product list module control and apply for the following changes. Please see Display Templates for more info. Look for the following lines below and add a Selected="true" attribute to the desired list item.
<asp:DropDownList ID="PageViewSizeDropDownList" runat="server" AutoPostBack="True"
OnSelectedIndexChanged="PageViewSizeDropDownList_SelectedIndexChanged">
<asp:ListItem Value="10" resourcekey="TenPageViewSizeListItem">10</asp:ListItem>
<asp:ListItem Value="20" resourcekey="TwentyPageViewSizeListItem" Selected="true">20</asp:ListItem>
<asp:ListItem Value="50" resourcekey="FiftyPageViewSizeListItem">50</asp:ListItem>
<asp:ListItem Value="100000" resourcekey="AllPageViewSizeListItem">All</asp:ListItem>
</asp:DropDownList>
You can also change the number value of the list items (e.g. from 10 to 100 if you want to change the available page sizes). You will also need to change the text for the resource key pertaining to your custom display template that appears on screen from the static localization. Please see Static Localization and Language Packs for more info.