My setups (in roughly that era):

Pentium 166 MMX, 64MB RAM, Matrox Mystique (mostly for 2D, with some special 3D titles), AWE32, Win 95 / DOS 7. In DOS, I run Doom, Duke Nukem 3D, other later FPS, later Wing Commander games, etc. In Win95, I run Warcraft II BNE, Mech Warrior II, some of the later Sierra Windows games, things like that.

Pentium II 350, 128MB RAM, Voodoo 5 5500, AWE64 Value, Win 98. I don't use DOS on this PC at all. It's mostly early 3D (GL) and later 2D games, like Starcraft, Riven, Worms, Quake, etc. This is a little heavy on the GPU side, but I had a few cards I wanted to use, and this distribution made the most sense for me. A Voodoo 3 would have been more "appropriate" had I not already had the 5.

Pentium III 1.0GHz, 256MB RAM, Radeon 8500 Pro, SB Live!, Win ME. Older Direct-X 3D stuff like RealMyst, Rainbow Six, etc.

My suggestion is for DOS games to use low clock Pentium 2 or 3 processors with an AWE64, and for Windows 98 games a Pentium 3 or 4 with a Live. To choose the clock you must consider the processing requirements required by the game, just as there are games that require a powerful processor there are others that do not need and may have problems such as crash or acceleration. Resident Evil 1 and Blood Omen for example need a processor running around 400mhz or less to avoid crashing, Alien Trilogy at this clock is very fast while Mortal Kombat running on MAME DOS needs a clock of at least 800mhz not to choke. In Pentium 2 and 3 there is the possibility of underclocking, in Pentium 4 not. As for sound an AWE64 is the best option for DOS if you are not willing to sell a kidney or want a bug free card and spending little money. Live, successor to 64 and now PCI, is the best card for Windows 98 considering sound quality and availability on the market.