Lots of great recommendations here. I’ll add some things:
Windows will be a great choice for something you are familiar with, but the current iterations are definitely heading in the direction of being advertising-filled messes. So it’s not a bad idea to look at alternatives.
Apple should be a good choice for a “just works” system without a lot of junk in it. But if you’re new to it there will be a learning curve. Software options are also more limited. AutoCAD looks to be your only major commercial CAD option there.
If you want to explore Linux, try a live usb stick and see what you think. It will feel very different and there will be a larger learning curve, but a liveUSB should be a risk free and relatively easy way to try it out and see if you love the difference or hate the change. If you still are interested at that point consider dual-booting or repurposing an older system for something to tinker with.
CAD in particular might be a sticking point. Windows will give you the most options. You didn’t mention whether you’re tied to a specific system as is common for a profession / livelihood or whether you’re open to options. If you’re able to look at alternatives— AutoCAD is on Mac and Windows, SolidWorks is on windows only. QCAD is a smaller option for 2D CAD on all three platforms and I’ve been happy with it for everything I’ve tried to do.
40 GB is pretty rough and personally I’d say about 120 GB is the lowest if you want some wiggle room without needing to frequently tinker with finding free space. But 500 GB is way more than necessary at least for now.
I’ve run into this before, it’s mainly that windows is bad at identifying “unmovable” files. Just delete it as described in that link, try the shrink again, and recreate after.
Usual caveats apply: no guarantees, make sure there’s backups or no critical info on the system, if this messes up your system it’s on you, etc.
But the creation of each additional bill devalues the currency. At some point the value of all this paper money is negative because it’s not worth keeping and storing. The point at which they cross from positive to negative value would give them zero value, and they’d be equal.
Cars (and seatbelts) are the biggest reason I see. Cloaks:
They’re great for pedestrians but not so much for motorists, cyclists, and motorcyclists.