What exactly do you mean by photo viewing? At home, on your smart TV, on forums/websites, mobile viewing, what exactly are you looking to do?
I have a Synology NAS myself, I've got it internet connected off my home network through my router. I use 2 factor authentication, and have the login set to 5 wrong attempts & it blocks your IP address forever. To discourage hacking. Had it for a year or two now, the log files tell me it must be working as it's registered no successful attempts so far. The 2 factor authentication is in the form of a sign code generated in an app on my phone, which makes it difficult to try. I've got the app on a couple of phones, it only allows 1 phone to use the authenticator at a time, the one that you allow access to. That phone lives in my pocket, so should be quite secure
Personally, I think it's the greatest thing I've ever bought. I'm not the slightest bit an IT expert, I'm in the steel fabrication industry as my day job, but even I can work this all out, set it up to work and access it securely on my Windows network, Chromebook & also a Linux computer. From anywhere in the world with an internet connection. Which is really handy, as I do wander around various countries on the odd occasion :)
I was using the Synology photo's app with albums to organise & view my photos, from any device with an internet connection, but of late I've just been organising all my photos in folders in the generic photo album directory from DSM on the NAS, and then creating shared folders with a link. You can share a single photo, like this andrewNASaccess.quickconnect.to/mo/sharing/vqlhPz092
Or an album with multiple photo's, like this andrewNASaccess.quickconnect.to/mo/sharing/z8Bg0qKtj
Or this andrewNASaccess.quickconnect.to/mo/sharing/NdqjxOXng
You can set up passwords, expiry dates, or a few other options depending on what you want to do.
For uploading to web forums, I've set mine up so it appears as a native drive on your system. On my Windows computers, Chromebook and Linux. I haven't quite figured out how to do it most securely on Linux, it seems to want to use SMBv1 as its Samba share protocol, it works if I set my NAS to SMBv1, but I'm not comfortable doing that. A bit more investigation required there. Hope this helps, like I wrote, I'm no tech expert, but given a bit of time I seem to be able to figure it out :)