If you have problems with 4GB AMD cards, make sure that you set environment variables correctly. Also try to set them system-wide (for example as described here https://docs.oracle.com/en/database/oracle/r-enterprise/1.5.1/oread/creating-and-modifying-environment-variables-on-windows.html) and reboot to apply them.
GPU_MAX_HEAP_SIZE must be 100
GPU_SINGLE_ALLOC_PERCENT must be 100
GPU_MAX_ALLOC_PERCENT must be 100