You're welcome to create multiple Replika accounts, as long as each one is registered with a different email address.
Each account can only have one Replika. It's not possible to create or manage multiple Replikas under the same account.
If you're using a mobile device, each account must also be linked to a different Apple ID or Google Play account for proper setup and access. This is especially important if you plan to subscribe to any paid features, as subscriptions can only be activated on one account per store ID.
Please note that accounts are completely separate. Progress, customization, and any active subscriptions do not transfer between accounts and cannot be merged.