Ok, here is my es setup, .emulationstation folder from /media/home/ on internal sd. My actual gamelist files are included in the respective system folders, you can reference the info in these when you set your gamelist/rom/image path in your scraper program of choice. Follow along Mashtec's video, he covers everything for scraping.https://drive.google.com/file/d/1LHQKRWsoKrG11m3IYBRXpe2MHqkRbOLy/view?usp=sharing
Here is my roms folder from my external sd, folder from /media/sdcard/, although that may be media/RG350/ if you aren't on Rogue. There are no roms included, the atari 2600 folder has an empty file named as a ROM and the corresponding boxart just to illustrate the path and format. Each system folder in roms has a boxart folder for boxart, other setups may use media as folder or have a different path entirely.https://drive.google.com/file/d/1-NBVT_tlwR9qleXeRxOGlhIuFC6bs1M0/view?usp=sharing
My setup has several thousand roms on a variety of systems, ES takes less than a minute to load. Boxart images range between 5-40kb each with no additional resizing/shrinking performed. So far my biggest complaint is the lack of favorites/custom collections, I have created folders named -favorites- in systems and added duplicate roms and boxart links, obviously less than ideal, but easy enough for a quick shortcut to my go to games. Once I have the time I plan on seeing what I can cobble together for custom collections, on my pi I have some nice "systems" for Mario, Zelda, final fantasy, etc. encompassing games from a variety of systems.
The only two errors I have experienced with my unit thus far is a duplicate entry for MGS in psx in EmulationStation, tried everything to remove and I either have 2 entries or 0 entries, and after a long session, 5 or 6 hours, played off the charger my battery level back in gmenu showed 100%. The flashing green indicator light did begin at (I believe) 10%, but fully charging and playing for a bit off charger still showed 100%. Power off and on didn't fix it, but resetting with the reset button got it back on track.