Keep in mind you’re not going to be able to run all games between those years on a single build. Quite a few older games need older hardware, especially slower CPUs. Then, the DOS support on ME has a ton of issues that broke many games (one of the reasons people hated it), and XP is needed for a lot of the later Windows games in that range.
That said, it should work very nicely as a 9X build, which also happens to be the era with the least emulation support. If an older DOS game doesn’t work, you can always use something like eXoDOS on a modern computer.
One additional cool thing you could consider down the road is something to really take your midi experience to the next level like an SC-55 MK II.
Yeah, XP would definitely have more issues. 98SE probably would have the best all around compatibility. But there are some Win95 games that only run on Windows 95. The computer you’ve got is really nice for the 1994 - 2001 era, though. What you could do is get a pullout tray, and have different drives with different loads, and switch them out as needed. Ultimately, if the games you want to play work, that’s what matters.