I've tried all 3 options: AdLib, Roland and Tandy.
AdLib gives a clear improvement over the default configuration. I don't see why GOG has not enabled it by default. Must be an oversight.
Roland sounds weird. It replaces synth sounds with musical instruments. The music sounds more pleasant than AdLib, but odd, since it clearly was designed for synth sounds. The sound effects are also played with musical instruments which is not good.
Tandy music sounds worse than either 2 options, but sound effects are a clear improvement, especially the engine sound that is done with noise instead of high pitch drone. Sounds much better, a bonus for immersion and the main reason why I prefer this configuration. Another downside of Tandy is that it restricts the graphics to 16 colors, but the game doesn't suffer much from it in my opinion.
For anybody wondering how it's done with the GOG installation. There are 2 files in the game directory: dosbox_f19.conf and dosbox_f19_single.conf. To enable AdLib sound, open dosbox_f19_single.conf and add " /aa" to the "f19.bat" line. To enable Roland sound, install the Roland patch (see above) and add " /ar" instead. To enable Tandy sound and graphics (you have to do both), add " /at /gt" to that line and replace "machine=svga_s3" with "machine=tandy" in dosbox_f19.conf.