I do not tend to do 100% period correct machines but generally I follow 3 principles when building a retro system:
1. what components were available on the market in that particular year or period.
2. how much ram the motherboard can take.
3. what Windows versions were on the market when those components were launched.
The most difficult period correct items to get are the hard drives! Believe or not but I had drives that I personally purchased died on me even without being mistreated in any way! I expected the motherboards and the graphics card to go first but no, I still have 20+ years old mobos that are running perfectly fine! On the other hand the CPUs and the RAM last forever if you do not drop them or short circuit them! IMHO using new brand names PSU is crucial so I never use period correct ones!
As an example:
2005: Athlon 64 X2 4800, 4*1gb Corsair (3.25gb recognized), Abit AN8 SLI, WD 500gb, geforce 7800gtx*2 - Windows XP SP3 flies on this system!
2001/2002: Pentium 3 1400, 3*512mb Samsung, Abit VH6T, WD 120gb, geforce3 ti500 - Windows XP SP3 performs much more poorly however still usable but (I know this will be considered blasphemy 😀 )with better performance than 98SE on this system.
2001/2002: Pentium 3 1400, 512mb Samsung, Abit ST6, WD 80gb, geforce3 ti500 - Windows Me because of the small amount of RAM.
2000: Pentium 3 1000EB, 3*256mb Kingston, Abit BX133 raid, WD 60gb, geforce2 pro - Windows 2000 runs very well.

I tend to overspec - or rather, back in the day I was intentionally slow with upgrading OS, preferring minimal features and max speed, to new features crawling. I ran Win3.1 till 1999 on my P60. Unless I'm trying to do something very time-specific, I'd choose software conservatively for my hardware. Yes, slow systems were a period thing, but having to use a 486DX-33 with 4MB RAM running Windows 95 at university cured me for life of wanting new OS on old HW 😉

I'll use whatever it takes, and can afford or find, to get my games to work! 😁

With a mix of rose-tinted nostalgia as the icing on the cake.

If we're assuming DOS & Windows here for general PC gaming abilities, I tend to do something like this -

8088 / 640KB RAM = DOS 3.x (my XT build currently runs IBM PC DOS 3.30)
286 / 1MB RAM = DOS 5.x+ (my 286 currently runs IBM PC DOS 7.0)

With regards to GUI for the above systems, I use either Windows 1, Windows 3.1 or GEM Desktop 3.13, but that's really just for the gimmick factor.

386 / 8MB RAM = DOS 6.22 + Windows for Workgroups 3.11
486 / 16MB RAM = Windows 95 (version depending upon CPU speed & HDD space, but generally I stick with 95B)
Low-end Pentium (133MHz or less) / 16MB-32MB RAM = Windows 95
Higher-end Pentium & MMX / 32MB-64MB RAM = Windows 98SE

I'd probably stick with Windows 98SE right through any AMD K6-2 / Intel Pentium II builds, as well as lower end Pentium III builds (500MHz Katmai or less). RAM would be between 64MB-128MB depending upon requirements.

PIII & Athlon 600MHz-1GHz+ range / 256MB-512MB RAM = Windows 2000 or Windows XP

I'd then use Windows XP right through any other builds up to around the Core 2 / Athlon 64 X2 era where I'd probably switch to Windows 7 for a dedicated gaming PC build and at least 2GB-4GB RAM. Any more modern systems would get either Windows 8.1 or Windows 10 depending upon specs. Note: I do have Core 2 & Athlon 64 X2 era PCs running Windows 8.1 & Windows 10, but they're not used for gaming, ie. they're general office based systems or HTPCs.

I don't really have any use for Windows NT 4.0 or earlier, except for maybe novelty purposes.

I haven't found a justifiable excuse for Windows 98 first edition or ME on any of my systems either, as they either all work great with 98SE or would be better suited by 2000 or XP. Vista will NEVER be used on any of my systems as even with the later service packs, the performance will just be better with Windows 7 anyway.

My approach (rule of thumb) would be something like this:

386 till 486 66MHz - DOS (and perhaps some version of Win3x)
486 100MHz to roughly Pentium 150MHz - Win95 if at least 32MB or so.
Roughly 333MHz is the beginning of WinME territory for me, making 98SE territory go from 166MHz up until about 300MHz. This roughly coinsides with CPUs going from 66MHz FSB to 100MHz FSB. If under 128MB RAM, then 98SE
If ±800MHz or more (except VIA), I might consider either 2k or an NLited version of XP if 512MB or more. I would probably use something predating XP if the build includes any internal LS-120 drives, but depends on how incompatible all of the specific parts and OSs really are (but the easy way out is to simply keep using my ZIP drives). For VIA s370 I'd probably stick to Win9x for any of their s370 CPUs.
If above 1400MHz (except Netburst) I will probably (but not necessarily) run an NLited version of XP. If 1GB RAM or above I will most likely use XP instead of 9x.
If AM2 or above (unless single core CPU build), I'll probably use Win7 instead of XP. If above 2GB RAM, I'll definitely consider Win7 instead of XP.

I've never got around to building a rig for any version of NT except maybe on a testbench, so can't really comment on those.
Also not sure about Vista. The few times I used it, I wasn't a huge fan but it would probably be alright for use these days.

The list for me would be:

8088 - 8086 - MS-DOS 3.31 or 4.01 (if you want windows try windows 3.0) (windows 2.0 isnt worth for me)
286 - MS-DOS 4.01 with windows 3.0 with multimedia extensions or 3.1
386 - MS-DOS 5.0 or 6.0 with windows 3.1 or 3.11
486 / Pentuin 90- MS-DOS 6.2 or 6.22 or windows 3.11 or windows 95 first edition
Pentium 100 - 233 - Windows 95 OSR 2.X only
Pentium (II) Pentuim III 233-1000 - Windows 98 or Windows 98 SE
above 1000 till Athlon XP would go for windows ME or Windows 2000
Pentium 4 / till AM3 Windows XP
Windows 7 - anything for 2010 till Intel skylake