It can depend if your GPU can handle higher rates vs screen resolution on 98se i use 1024x768 it allows more hertz such as 75, 85 and so on; higher screen resolutions lower hertz.
But LCD don't support more than 60hz FYI if your trying LCD (without overclocking)

Its not the monitor, its the gpu drivers.

Some higher values wont be visible on win98, but can be unlock either with reg tweaks or software. I use 1920x800 and win98 tips at 100hz, 120hz works fine if unlocked. And yea makes a difference even with mouse movement

Thanks, gents.

I'm running a Frankenstein build. LGA775, with a Celeron 420 / Radeon X800 GTO along with its last windows 98 drivers. I carefully chose this build to have the least amount of conflicts, without paying the price tag of failing Win 98 era components. It has been great so far.

Is there a guide on the reg tweaks, if this is the route I need to go down to get high refresh ?

Look here, this is prob the easiest.

I found the main official driver inf from AOC worked on 98, and all the refresh rates show up and are selectable. Sadly, it doesn't actually change, though. The monitors OSD read 60hz no matter what I change it to. I even edited the inf so the minimum refresh was higher.

I then tried HZtool and Powerstrip, from the thread you linked, but still no go.

Dunno whats happening, as far as I remember I had different refreshes on x850, but its for sure a gpu thing, default plugandplay driver for monitor should be more than enough.

If nothing works, switch to xp, card works better there anyway.

XP isn't an option here. This machine is strictly for 95/98 gaming in mind. The card if fully compatible with 98. I run XP era games on my main PC. I'd just stick with a locked 60hz if I must, but it would be nice to get the higher refresh working.

Just not sure why it dislikes this monitor. I tested a 100hz + CRT on this exact machine (same card, drivers, os) a few months ago and it worked fine.

Still having this issue, unfortunate. Can't think of what else to try. Spent so many hours trying.

Please feel free to share a possible fix if you may know of one. Thanks.

Use PowerStrip to add more refresh modes.
What cable are you using (VGA/DVI/HDMI) ?

I have tried Powerstrip, HZTool, and adding refresh rates manually via the monitor inf. Neither has worked. The options show up and allow me to select, but the monitors built-in menu still shows as 60hz.

I am using VGA. This card also has DVI, but my monitor is only DP,HDMI,VGA. I did actually try with a DVI to HDMI adapter just to test if it would work, but the issue remains, sadly.