Maybe it's not relevant to answer the original post right now, but still maybe someone requires to read this. The problem with lags may occur because of:
1. Suboptimal power management setting in BIOS. Power management is extremely important, especially for any kind of PU (GPU or CPU). If your settings are set to certain values it may cause problem in such system as macOS, cause it prefers to decide on it's own what to do with your hardware and hard setting can be a problem in some situations, at least some setting related to GPU - especially. That's my experience. "Normal" options in BIOS aren't equal to "Auto" or stock suggested options that are written in BIOS and behave differently. Only Auto options related with clocks and power management make it possible for macOS to rule over your power wisely as it see fits.
2. Problem with certain macOS release, configuration of your bootloader, vendor of AMD. I didn't saw what vendor author is using, but the best option is definitely Sapphire for macOS.
3. I didn't saw if author really determined that the problem occurs only with this GPU and there is no problem with his build with another GPU. Didn't read the whole thread. If the problem occurs with any GPU with his build, then I can suggest to force DDR profile in BIOS instead of "Auto" options or extreme profiles, since it can lead to some very weird kernel panics or behaviour.
4. Also I didn't noticed what exactly animations are suffering from lags. Maybe it's more related to CPU/IGPU enabling. I remind you that original macs doesn't have a possibility to "disable in BIOS" IGPU, so Apple Developers in some cases count that IGPU is always enabled and they use it in software development.
Hope that this can help someone to start diagnose their hackintoshes with the similar symptoms.