The images can be on DropBox, no problem. It's just not suitable for the database.
GOAL - is for my 2 grown daughters, and perhaps other relatives to access the family photos (from their homes),
IMWS can technically do that (and does so, reliably, in HOME or corporate networks).
The "load" on your PC would also be small, because IMWS is very efficient. Running it with a couple of users doesn't require much performance.
To allow others to access your image collection from the "outside", you theoretically only need to open the port IMWS is working on in your firewall, allowing "the Internet" to access your PC.
Everybody who knows the IP address of your PC (or the URL if you use a DynDNS service) can then access your image collection via IMWS, using only a web browser.
But there is one problem:
SECURITY.
We live in harsh times and if you open your computer to the Internet, bad people and automatic 'bots' will try to break in. Trying to make your computer part of an illegal bot net, spread viruses, send millions of SPAM emails and whatnot.
It's very hard these days to make this secure and I can only advise against it. Doing this safely needs specialist know-how, setting up a VPN etc.
All well for typical corporate users, but not something a 'normal' user will/can do.
There are so many free and paid ways to present photos on the Internet these days. From Facebook to Instagram to smugmug, Google and Amazon photos ...
You can usually just drag and drop images from IMatch to your web browser to upload and fill your online gallery. And the hosting company takes care for security and your PC remains safely behind the Windows firewall.