Figured I would qrite this quick post to save people a lot of time and trouble if they're like me and want all of the mods to work — at the moment, Fabric 0.13.0 is being bothersome when using BedrockIfy, Architectury API and OptiFine in conjunction.

To resolve this, stay on 0.12.12 until both BedrockIfy and Architectury API devs have committed fixes which are compatible with OptiFabric / OptiFIne. If you need a mod using Fabric 0.13.0 specifically then seek an older copy using Fabric 0.12.12 which will not conflict with your other modifications.

Feel free to let others know if this is resolved in future! Due to the nature of this writ, it should soon become deprecated and obsolete advice, of which I will provide notice if this is the case.