Is there an "ideal" order for effects?

Particularly ones that have to do with sharpening and anti-aliasing.

There is a noticeable difference when I move them around, yet I can't quite put my finger on it. So far I've found only one discussion about this, but it didn't have a definitive answer. Is there at least a conventional order for certain effects that yields the optimal image quality, or is it purely a matter of taste?

It's really just step-by-step based on what you want. Effects near the bottom are loaded first.
Example:
At the very bottom I have the color adjustments (a LUT in my case).
Above that, sharpening, because I want to sharpen the 'final' image that has all the color adjustments.
Finally, filmgrain at the top, because I don't want to sharpen the grain.

For your AA and Sharpening, I'd go:
First, at the bottom, your AA of choice to smooth edges
Above that, sharpening to reduce the blur of AA.
-If you sharpen *before* AA, what you're sharpening is the jaggy aliased edge that the AA filter works on. Sharpen edge -> Blur the edge with AA. Counterproductive in my opinion.

In my experience, sharpening after AA often brings back jagged edges that were blurred by AA filters (However, this may be depended on sharpening algorithms. As I mainly use LumaSharpen, that is what I've observed. Other sharpening filters may behave different). Turning up the sharpen strength a bit and putting it before AA seems to look better to me. But that's just my two cents, of course. I think in this case it's just a matter of taste.

Effects are applied from top to bottom, not bottom to top.

..?!
*tests*
Hey, what do you know? I had it wrong.
Yes, top-to-bottom. Think of everything I said, but in reverse.

FierySwordswoman wrote: Effects near the top are loaded first.
Example:
At the very top I have the color adjustments (a LUT in my case).
Below that, sharpening, because I want to sharpen the 'final' image that has all the color adjustments.
Finally, filmgrain at the bottom, because I don't want to sharpen the grain.

For your AA and Sharpening, I'd go:
First, at the top, your AA of choice to smooth edges
Below that, sharpening to reduce the blur of AA.

Did I get that right?

Yeah. That's how I'd do it.

Note: I always use AA from my GPU control panel (if the game doesn't have it), as I've found it works better for my tastes.
FXAA, with some MSAA if I can spare the performance.

IIRC, forcing AA in driver is not recommended when using ReShade.

Yes there was this initial thread here:

reshade.me/forum/general-discussion/2387...-ordering-discussion

And though I said I'd get back to it, in my testing also, in every single game, doing sharpening->AA looks better. It's quite easily noticeable in all cases too.

As for the rest, add to the thread!

"Forcing AA in driver is not recommended when using ReShade."

Why would that be? I do that for every game that doesn't have an FXAA option (adding MSAA in the case of certain games), and have used ReShade versions 1-3 over time with no ill side-effects that I'm aware of.
I've found that forcing AA/AF through my GPU panel has never had any issues, excepting in Warcraft III where the trees break when 'Negative LOD Bias' is automatically set to 'Clamp' after forcing AF. Manually setting it back to 'Allow' removed the issue, allowing me to keep 16x AF.