No, for the real sound card DirectX (if you are on Windows) handles the sample rate conversion so everything should be right. SDL which DOSBox uses for audio has far from alright sample rate conversion.
Anything but 49716 on both mixer and OPL, sounds distorted and noisy. This applies to the Fast/Compat modes as well as for Nuked.
Real OPL3 for reference (YMF719):
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Awesome stuff! I'm currently listening to MegaRace's music right now and it sounds perfect! At first, the song "Maeva" was playing weird but it turns out I had the oplmode set to "opl3gold" (which I turned on earlier for my reverse engineer work on Dune and MegaRace's music format). Everything went back to normal once I switched the oplmode back to "opl3". Keep up the excellent work!