I don't have much to add to this that hasn't already been mentioned. You'll definitely want to try and seek out a combination of a board with BIOS options for overclocking and an unlocked CPU. Otherwise you'll kinda be stuck using external software throttling utilities for DOS software bound to the frequency of your CPU.
As obvious as it sounds, it sorta depends on what you plan on running in DOS in the first place. Stuff like Stunts runs great on my own Athlon XP dual boot 98SE/XP setup, but other stuff I have like the Even More Incredible Machine absolutely requires some sort of throttling utility or just a slower computer overall to run correctly. Not having access to any sort of CPU multipliers in my M7 VIG PRO's motherboard really limits my options on that machine. If you don't plan on playing anything that's sensitive to CPU clock (usually reserved for early DOS games, with exceptions) your current planned build should be fine for your needs.
As for your sound card, I would highly recommend using your SB live, or any PCI sound card, over your on-board solution. It should improve the performance of your machine, most notably in windows 98 & 98 games. [Edit: I just read that you have sourced your own drivers for using the card under DOS, so feel free to disregard the following if they work for you] Phil's Computer Lab did a video on those CMedia CMI8738 PCI sound cards, which feature very poor 3d audio support but have the capability to emulate old soundblasters, with somewhat mixed results. They are incredibly cheap cards however, so it may be of interest to throw into your build. It does a better job of emulating a soundblaster than those PCI soundblasters do IMO.
Some motherboards also have an interface for a PCI soundblaster known as soundblaster link solely to enable soundblaster 16 support under DOS, but I have no experience with any soundblaster link devices myself and cannot attest to their performance. I believe it requires a unique cable to work as well, no clue how common they are or how to make one. SB Link may also predate the era of parts you're assembling, I'm not entirely certain myself. Disregard this entire thing, upon further research it appears that you can just use software to enable the same functionality, so there is essentially no point in even bothering with the interface from the looks of it.