You can probably still use most of the functions but you won't be able to use list_my_accounts or get_account_history

account_by_key doesn't use a huge amount of memory, so you can leave it enabled if you want. account_history does use a lot of memory, but you can eliminate almost all of that usage by only tracking your own account with --track-account-range

However, if you are running a witness node (signing blocks) you should not use any extra plugins, even these. Better to run another node for wallet purposes if you need it.