Hey guys, I got it fixed.
On my Wife's computer, which is a real mish-mash of parts (AMD 8350 FX on a MSI 970, with a 3060Ti, older SSD and brand new PSU but ancient Case and older/used motherboard/CPU).
Fresh install of windows, only Steam, Stardew and a couple other games for testing on it.
All of the other suggestions helped in increments. It went from crashing/freezing to Stuttering bad.
Stuttering bad to stuttering a bit.
Stuttering a bit to only stuttering when I'm clearing out a large amount of crop(or fiber on a new farm).
One user suggested putting some code into the boot-up settings of Stardew, when going through steam(which I did do).
It all made a difference but I started to wonder if it's to do with compatibility issues- new Windows OS's have advanced, various visual settings you can set(For example, the toolbar on the bottom is see-through by default on W10). I didn't actually change the visual settings before I fixed it- it got me thinking:
Stardew isn't a demanding game, what if you just run it as/with earlier Windows versions?
TLDR:
---->Right click Stardew. Go to properties.
----> Go to compatibility.
---->Set to compatibility mode for Windows 8(If this doesn't work, you can try W7, or W10 if you're on W11, etc. etc.).
Done!
Other things I did:
- Set Power mode to performance(I've had strange issues with radically different games with this setting). Power-saving can often cause problems, and Balanced in rare cases do as well.
-Turned off Vsync(This has caused issues with previous windows/games combinations for me).
-Using the same method above, set Stardew to "Run as Administrator"(It's in the same menu, just lower down).
-Edit this post twice
This computer doesn't have an on-board that ConcernedApe mentioned could be turned off/on/Disabled, so I really think the issues lies somewhere in the realm of power/video/display adaptation.