I am thinking thru changing to a small Eurorack setup, mainly for effects or modulation downstream of a standalone synth. Sounds like blasphemy for some here I imagine, but hear me out....
I have a Mother 32 and been exploring that over a year. Built a 6U 84 HP case and bought uZeus power, added another VCO, a Doepfer ADSR and a VCA since the M32 is limited in this regard, bought a MI Tides and an MI Clouds, an x4 attenuator. Before adding more and going further down the financial black hole, I had an epiphany that I liked the core Moog sound of the M32 but would probably just be as happy with a monosynth with lots of 'tweakability' like the Moog Sub 37 and some effects downstream. Patching a bunch of modules and getting some wacky sounds was fun at times but was frustratingly tedious when I wanted to just "play".
I sold off a lot of my modules. M32 will probably leave but still have for time being. I plan on keeping the Clouds, Tides, and x4 attenuator within a single 84HP rack. I think the next order of business is adding a random source like the WoggleBug to get some randomness going while modulating the Clouds. I have stompbox delay and reverb in my guitar rig that I use currently, but I might want to add some dedicated Eurorack modules to keep my guitar and synth stuff completely separate. Granular stuff like the Phonogene and the Nebulae seem very interesting to me. Has anyone else gone this route - essentially using Eurorack for effects with a standalone synth (and not a "semi-modular" synth)? I'd love some ideas or thoughts on what others have done.

Check out the Moog Grandmother or the Matriarch. I don't think they are going to sound like the M32 but they do have that Moog sound. Both are semi-modular compatible but don't require any patching to work for your most basic sounds.

If you're looking for polyphony, patch recall and so forth... a traditional all-in-one synth would definitely suit you better. Most stand alone synths operate at line level. Eurorack operates at "synth level" which is a lot hotter... more volts... than line level. So if you want to use Eurorack to process your sound then you'll want some line to synth level converter to go into your Eurorack and probably synth to line level to get into the rest of your set-up. There are a lot of ways to do it, but this is the sure-fire way. It is possible to also sync your stand-alone synth to Eurorack components. Some forward thinking synths have CV and gate outs. Others you'll have to find a MIDI to CV converter to go from MIDI clock to eurorack clock.

There's nothing wrong with finding a pure Eurorack set-up not-for-you. You hit the nail on the head when you wrote that it's not worth it to spend so much time tweaking modules when you want something that is relatively simple most of the time.

Thanks Ronin. I really wanted to like the Grandmother when it came out because of the price point and patchability. Some demos sounded pretty good, but when I got a chance to tinker with one here locally, I just didn't care for it. Some of it was very specific things, like the filter behaves very different than other ladder filters and it was harder to find the sweet spots in it, but mostly just didn't care for the rawer sound. I prefer the Sub Phatty / Sub 37 smoothness, even if darker and more subdued. The M32 is its own thing but closer to the Sub line than anything, to my ears. Presets are nice, polyphony not an expectation for me. If the CV equipped version of the Sub 37 is within my reach that might be the best bet.

You raise an interesting point about line level. Clouds has a gain input so you can adjust incoming audio; I suppose I can see how far that will get me first though.