From my experience: with regular tasks even more taxing than OP is going to use his mac I have never put enough pressure on 8GB to force MacOS to cache (this is NOT Windows for god sake). Don't forget about Maverics which brought memory compression and optimisation, process sleep etc..
Trust me again: Apple is much, much smarter with memory management than Windows (where this fear/prejudice originates I suspect). I highly doubt OP could flood 4 GB RAM (current MacOSX) with Word/Excel/Mail/Safari combo.
BTW: MacOS is using all ram available at all time. Please find attached Activity Monitor for 8GB, 16GB and 32GB Macs (I've just made those snaps from Macs I have available at hand) - all of them were taxed to a medium level (Office/Mail/Safari + some other apps):
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Believe you meant swap, not cache there.
I am normally not one to defend Windows, but I have to here. Windows in no way uses more RAM than macOS. In fact, on a clean boot of both, macOS will have 700MB more RAM wired than Windows on my iMac.
"Maverics which brought memory compression and optimisation, process sleep etc"
All of what Mavericks brought to the table both regarding processing and memory optimisation, is also available on Windows, including memory compression.
When it comes to memory management, there is one thing I'd say macOS does way better than Windows, but it's a mostly subjective thing and not an objective fact that it's better. It depends on how you use the computer.
macOS loves to use RAM. Got 16 gigs but you're only using 4? Well let's fill the rest with things you might want to use in future. We'll leave a bit of buffer space so if we predicted wrong, you'll still have some memory to put your files in.
This method is brillant, since a lot of the times, your data is already in memory before you need it.
The downside however, is if you need to open something massive that was not what the system cached for you. The penalty is rather small, but there is a penalty, in that you then have to flush the data before you can repopulate the memory with the correct data. By default, Windows only populates memory with active tasks. Regarding usage however, Windows itself uses less memory than macOS.
Personally, with medium-light usage, I fill 5 GB of memory. Now that's not "5GB of 'used' memory". It's 5GB of active memory. So I'm not counting the cache, only app memory and wired memory. This is Mail, Spotify, Safari, System Preferences, my MenuBar applications and that's it. Albeit that this is on a 5k screen, so visual assets stored in memory will take up significantly more memory than on normal-DPI screens. (bitmaps, not vector graphics).
Now if we go five years back, we're at what? Lion?
Think about how much, not necessarily macOS itself, but the apps that you run on it too, have grown in terms of memory footprint, from Lion to Sierra. Is 8GB enough right now? Yes. Definitely. But 5 years down the line, it'll still be enough, but not "plenty" as it is now. You'll start having occasional swaps to disk and you'll lose all the benefit of caching files to RAM since your active RAM usage will take more space so there'll be less for caching.