The option MBEDTLS_ECP_FIXED_POINT_OPTIM now increase code size and it does not increase peak RAM usage anymore.
If you are limited by code size, you can define MBEDTLS_ECP_FIXED_POINT_OPTIM to 0 in your config file. The impact depends on the number and size of enabled curves. For example, for P-256 the difference is 1KB; see the documentation of this option for details.