Thanks for your reply.
I was trying to avoid having to install stuff unnecessarily on my nice clean installation, but never mind.
For other potential users of ShadowFX:
I tried ShadowFX out and it does exactly what I hoped:
blur 0% | Transparency 0% | 3px on all sides | blue colour gives a high visibility border around all windows and programs.
Bonus - unfocused windows/programs can have a different colour and less prominent border! Excellent!
It does need to stay loaded and runs as a service. It seems to use 1mb of ram and pretty much zero CPU. On install, first reboot/load took slightly longer. Subsequent reboots have been fine. In my opinion, ShadowFX on its own is much less likely to be broken by a Windows update than Windowblinds, and it must surely use less resources (adding only shadows as opposed to theming everything).
I noted that folders were 'ejected' from within Fences and onto the desktop after I installed ShadowFX and rebooted. It might have just been a coincidence. No big deal for me, because it was just a few folders. But if you have lots of folders organised in lots of Fences, watch out. Fences has a snapshot feature that might help if this happens though.
Here's my own little FAQ about licensing and support, because it took me too long to figure out the details:
As of July 2019, the way the licensing works for all these individual programs is that you get incremental updates for v1.xx (for example, when Windows updates break the Stardock enhancements), but if v2.0 is released, then your v1.xx basically becomes abandonware, receiving no further updates. So be aware that if you buy v1.xx now, you might have to pay a reduced price to upgrade, and this might just happen to be around the corner.
This seems to make some people angry when they're caught out, but if you buy these apps knowing how it works, then it's really no big deal. I've just bought Fences, Start10 and ShadowFX, which make Win10 bearable to use, and I'm fine with paying for upgrades if they happen to occur in a couple of months time, because I know that it allows the software to be maintained and protected against Microsoft updates.
The other alternative is to purchase an annual subscription to Object Desktop (currently about 20$ per annum), which gives you access to a large suite of the apps, along with incremental updates and version updates. The big caveat here is that if your subscription lapses, although your apps keep functioning, you immediately lose access to all future updates, including the incrementals. Further, you also lose access to your downloads, so you must have the individual apps and licenses saved locally if you intend to unsubscribe from Object Desktop (although IMO there's not much life left in the apps if you can't update them). In other words, the licenses obtained through OD are not like the licences for the individual apps - you cannot get any updates if your OD subscription lapses.
The license keys allow you to install any app on up to 5 computers simultaneously, whether individual apps, or downloaded through Object Desktop. You can therefore easily transfer apps to a new computer too. However, it also means the software probably phones home, so Stardock can keep track of how the licenses are being used (some companies buy one license and then try to use it on hundreds of machines). So be a little bit careful with your installations, otherwise your license key(s) may cease to work on one or more of your computers. Again, this seems to anger some people when they're caught out, but if you know how it works, it shouldn't be a big deal.
Lastly, people complain about lack of support. Most of the support is given through the forums, and mostly by users/volunteers/community assistants. Stardock only provides email support for the following:
-Refunds \ Incorrect Orders
-Email Changes \ Account Merges
-Corp Sales Where Support Was Purchased
-Object Desktop Subscriptions (support is included)
-Media \ Partnership Inquiries
For any of these issues, you NEED to create a ticket which, from reading about complaints, admittedly may take a day or two for a human reply, and perhaps most of a week to get the problem sorted. But many people appear not read the part about the ticket at the bottom of the first automated response, so they don't even create one, and then get angry when their original email enquiry is 'ignored'. Also, spamming your own ticket by replying to yourself does not result in your issue being put to the top of the support list.
That's everything I learnt, I think. Enjoy your software!