Yes, there are three 5mm spacers and one 15mm spacer below the stem, so I have 30mm of adjustment range in 5mm increments. However, I have a carbon fork, and from what I have read, I can't drop the stem by more than 5mm without cutting the steerer tube, which is a permanent change. (Cannondale actually warns against using any spacers above the stem, but I think 5mm should be safe, since this is often recommended). In contrast, flipping the stem is a massive 20mm change, but is reversible and only takes 5 minutes at home.

What is the order of the changes that you recommend? With the combination of one spacer and stem, I can drop 5mm, 20mm and 25mm without cutting the tube. More than 25mm (along with 10mm and 15mm) requires a cut.

Edit: After doing more research, it seems that the top cap is integrated with the expander plug, and is designed to be used with no spacers on top. Lots of Cannondale owners report no issues running spacers on top, though, so I think it is fine as long as I properly torque the stem bolts.