We have analyzed your query. Please find the below response for your queries.
Query 1: When I configure a Treemap with Drilldown feature, I have Child Items which are Leaf Items (with no children) But the + Sign is still displayed and I can click on it.
We have prepared a sample based on your scenario. In that sample, we have only one parent and that has two children (leaf items) and the children has no children. And + sign will be displayed for that parent. If this is your scenario. we would like to let you know that, this is a behavior. When drilldown is enabled and if parent has any children then + sign will be displayed for that parent. Kindly find the below screenshot for your reference. If this is not your scenario, kindly revert us by modifying our sample or provide your code sample and screenshot which will be helpful in further analysis and provide you the solution sooner.
Query 2: because it is a leaf item, this Item takes the full size of the rect which is not really necessary to display because it's a Leaf Item.
We are not aware of exact scenario of this query. The leaf item will take the size based on the weightValuePath. So kindly revert us by providing a screenshot and code snippet for this scenario.
Sample for your reference, can be found from below link,