Hello Sweta.
Merge node (class) has to be implemented for any enhancement developed for Accounts. There is no standard implementation/configs for this. Because it's a custom logic. And SAP don't want to be in charge of it. Check note 1836295 - BUT000 AET tables not merged when executed Account Merge
Restriction of transaction type should be done on project basis as well as far as I know. Just copy the standard node and adjust its class accordingly.