After literally years of trying different combinations, I’ve finally settled on the Columns view for most purposes. I prefer the appearance of the 3-panes view, I don’t like the way it “hides” subgroups from the list of contents. What makes Columns more palatable is the Quick Look window. I assigned a space to DT, stretched DT’s main window out to four columns (with room for the Groups panel on the right) and limited it to the top half of the monitor screen. The bottom half of the screen is reserved for the Quick Look window. Now I can see the contents of a file while I arrow up and down through the list of files in the active column. Works great for me!
It would be nice if DT remembered the location of the Quick Look window as it does the Groups panel; as it is I have to resize and reposition the QL window every time I relaunch DT. Also, I wonder why viewing in QL leaves a file unread and why Next and Previous files as well as their menu and keyboard cousins are greyed out in Columns view.