Emulator.JS works by loading the emulator and rom directly in the web browser.
As a result you can easily setup a system like Romm to host all your roms on a local NAS, then you can load them up on the AVP to play whatever Emulator.JS can support. I know there are also alternatives built on the same framework, such as the recent JellyEmu that integrates it directly into jellyfin. I'm using Romm for this example.
It downloads the rom to the device (such as your AVP) and then it's ran locally. This means your NAS can just be a storage system and doesn't need any fancy hardware to do emulation. I assume this works better on M5 AVPs but this is footage of me playing a PS1 game on my M2.
Enjoy my terrible gameplay of Toy story 2 on the Ps1 as a example. These systems are 100% free and require no fancy subs or anything to setup and go.