Hmm, your specs should be fine, a 5600G with 32GB is plenty, and the GPU isn't really involved here.
Very likely the Chrome/Firefox difference you noticed might be the biggest issue. The app plays each GIF as a normal <img> and lets the browser animate it, and Chrome handles many simultaneous animated GIFs much worse than Firefox does; it's main-thread work, so it's a browser architecture thing rather than a hardware thing.
Two things worth checking in Chrome: make sure hardware acceleration is on (chrome://settings/system), and have a look at chrome://gpu to see whether it's fallen back to software rendering — that would make it much worse than normal.
Also, how big are your GIFs in pixel dimensions? 70 large ones (say 800×600+) is a lot more per-frame work than 70 small ones, and that matters more than how many are in the folder. If they're big, shrinking the window or zooming out so fewer are visible at once will help a lot, as will the pause-all button.