I can't say I ever used the SB emulation in DOS much, if at all to be honest. I used it purely for watching (listening to?) demos and coding them.
Now that you mention it, I remember doing the same thing with the DRAM

It's funny that you mention having a K6-II because I ended up getting the K6-III.
The SB emulation was not done in hardware but by a driver TSR. There are a number of problems with that.
First, it did tend to use some additional CPU which, while discouraging, was not the end of the world. Next, it(FM emulation) just sounded different... Some instruments sounded better, but usually at least one would just be really off making the whole thing sound bad. Or the timing or cadence would be off. Again, not a show-stopper... FM stuff never sounded that good anyway.
Probably the bigger issues were that the TSR would tie a chunk of that precious 640K making it difficult to run some 16bit stuff or just made some programs prone to crashing.
Also, I could not find stable windows drivers. I also seem to recall the TSR conflicting with windows.
A lot of people did what I did and installed both SBpro and GUS, but because ISA could not share IRQs it was a PIA finding a combination that worked and you usually ran out of IRQs long before you ran out of ISA slots.
It was great hardware spec wise, but ownership was overall very disappointing. True, there were a few demos and trackers that sounded fantastic, but that was also kind of discouraging to get a taste of what the hardware COULD do... if it only had support.