So far, everything I've tested on the Retroid Pocket 2 Plus when it comes to N64 emulation, I'm getting the best results from M64PlusFZ. I use the M64PlusFZ Pro app on my phone and RP2+ but the regular app can be optimized in the same way. On the original RP2, I used mostly RetroArch and N64oid but it looks like M64PlusFZ is the way to go this time. Make sure to delete the stock M64 app that came with the RP2+ and install the app clean from the Play Store which includes updates specifically for the RP2+.
Overall, I was very pleased with my tinkering and could get good results even at 2X with some games but there are still issues in games with bugs apparently caused by compatibility issues with the GPU, but are improved by getting the latest Play Store M64PlusFZ app. I came across a Reddit thread by FZurita (the developer of the emulator), tried out his suggested settings, and they beat my best tries so I'm going with his setup for now.
Best Optimization across the board for games:
1. Navigate to Profiles and select Emulation.
2. Select GLideN64-Very-Accurate and select Copy.
3. Give it a custom name and hit OK.
4. Enable "Use Fast Shaders"
5. Set "Use Native Resolution Factor" to 1X.
6. Go to Profiles and Select Profiles and select the custom profile you made.
7. Under Shader Settings, enable FXAA shader at 1X.
While these settings aren't the best possible settings in all games individually, they definitely give you more balanced performance across the board.
The Retroid Pocket 2 Plus is currently the best deal in budget retro handhelds and available for pre-order at GoRetroid.com. I'm nearly done with my initial review of the handheld and should be posting it on Wednesday.