The Tabs component doesn't handle many components very well. If I have any repeating list, such as the DataGrid or DataList, with like textboxes in the columns, it will take lots of seconds to switch tabs. The RenderMode doesn't change a thing. Please refer to this thread.
Also @enchev, recently I did some research on this and found out many ways of toggling elements visibility. There is the display (none:flex) and the visibility (hidden:visible). I tested showing the tab content with these properties when switching tabs and the contents were shown instantly. I'll create a test app to showcase what I mean.