I noticed that my GBA games were running just a tad bit slow at times as well. I am also using a Pi Zero W with Wi-Fi and Bluetooth on. The music wouldn't slow down but when playing games like Super Mario Advanced 4, it felt like Mario wasn't as responsive as I remembered, playing on my Gameboy Advance SP. To test it out, I pulled up the same game on my Pi 3 and FPZ at the same time and watched the in game timer count down. I noticed that the FPZ would eventually loose sync with the timer on the Pi 3, especially when moving around the level. I changed the V-RAMLimit on my FPZ through the Retropie menu from 100mb to 250mb. It seems to have made a difference when playing gba games. It feels smoother to me and I got the timer to sync up with my Pi 3. I'm not sure if there are any negative side effects in doing this on other systems yet but I did test NES, GBC, and GB with no noticeable differences. I will update this if I come across any issues with the new V-RAM limit. -Matt
(Update): One important thing to note; my Pi is not currently connected to any Wi-Fi or Bluetooth networks. I am currently at my college dorm, so I don't have anyway to connect my Pi to the Wi-Fi without having to jump though hoops to get it connected.
(Update): I found that with the VRam at 250mb, the UI of Retropie was a little slow. Setting the V-RAM to 200mb is the perfect sweet spot given that the Pi Zero only has 512mb of shared RAM between the CPU and GPU.
(Update): One important thing to note; my Pi is not currently connected to any Wi-Fi or Bluetooth networks. I am currently at my college dorm, so I don't have anyway to connect my Pi to the Wi-Fi without having to jump though hoops to get it connected.
(Update): I found that with the VRam at 250mb, the UI of Retropie was a little slow. Setting the V-RAM to 200mb is the perfect sweet spot given that the Pi Zero only has 512mb of shared RAM between the CPU and GPU.