To achieve your requirement, you can set the InitialSelectedLayout property of the dialog to Details.
dialog.InitialSelectedLayout = Telerik.Windows.Controls.FileDialogs.LayoutType.Tiles;
When using the RadFilePathPicker control, you can get the shown dialog via the DialogOpening event. In the handler, you can get the dialog via the Dialog property of the arguments, and set its initial layout.
I hope this helps. If you have other questions, please let me know.
Virtual Classroom, the free self-paced technical training that gets you up to speed with Telerik and Kendo UI products quickly just got a fresh new look + new and improved content including a brand new Blazor course! Check it out at https://learn.telerik.com/.