To restrict the number of items shown in the list, you can pass 2 parameter startIndex,length like this
<List items = "{path: 'model>/Invoices', length: 3, startIndex: 0}">
Can we make the length come from model length:'model>/property'
or is it possible to pass js variable into xml
the List supports a "growing" feature where you can surely use binding
see https://sapui5.hana.ondemand.com/#/entity/sap.m.List/sample/sap.m.sample.ListGrowing
If you really, really want to cut of more than x Rows, you could set a limit on your Model. see setSizeLimit