lots of interesting details in the faq https://www.polymega.com/faq/
I've seen some speculation that the emulators are mednafen based?
e.g.
"The team at Playmaji has spent a good amount of effort on a piece of technology called Active Cartridge Reading, an experimental subset of Hybrid Emulation that allows you to use any games or peripherals that work on a real classic console using a live blend of software-based emulation and memory mapped hardware. This technology, while it exists, is not yet fast enough for some of Polymega’s supported systems, and would result in a degraded overall experience if launched prematurely.
Now, support for game cartridges with on board DSP chips such as Everdrives, Starfox, or live-reading of devices like Game Genies is blended.
First, we’ve licensed standard DSP-compatible emulators for systems with those types of cartridges, which will allow games with special chips to be played via software emulation. That means you can now play backed up games such as StarFox and others regardless of whether you have the cartridge inserted, a convenience that most gamers will appreciate. We’ve also added a software-based Game Genie and Pro Action Replay as a reward level for supporting the console beyond its initial funding goals. The Super Game Boy is no longer compatible with the EM02 SNES SFC module, however, we have set up a GB / GBC / GBA module as an additional reward tier if reached.
Second, certain systems are going to be FPGA based. The first example of this is going to be the dedicated Famicom module, which will be released after the launch of the system. Famicom is particularly important to be implemented in this manner as it included accessories such as the Famicom Disk System (FDS), which was a critical part of its library and one that we will not be creating a dedicated module for. The tech to support FPGA modules is built in to the launch version of the Polymega™ Base Unit, and we may continue to release other FPGA modules in the future. FPGA modules will have a slightly higher price point than standard modules.
This decision / change overall has freed up our team to focus on matters that more factually push the needle in terms of overall system compatibility, as evidenced by our recently-announced support for the Sega Saturn, adding over one thousand new compatible games to Polymega™. What made this possible is that by removing the larger size FPGA from the base unit, we were able to opt for a higher clock-speed dual core chip rather than a slower quad-core chip for the main CPU, which now opens up the door to more demanding systems like Saturn, N64, Dreamcast, and more — which is what many people have expressed to us that they want."