I use the free Video Station plugin that comes with the Synology NAS.
We have hundreds of movies and thousands of episodes of TV shows (I own all the media, boxes and boxes of it) and subtitles are not a problem.
We had to play with audio codecs to get it working using the Mac, Android, iOS ad Apple TV apps, but we rip to MKV and get everything perfectly, up to full HD.
The browser experience is good, my son watches on his Chromebook.
It is a seamless experience, automatically pulling in Wallpaper, graphics and notes.
A good experience, it is used daily from multiple devices.
VERY pleased with it.