Below are some useful sfdx commands for retrieval
sfdx force:source:retrieve -m CustomField:ObjectApiName.FieldNameApi
eg:sfdx force:source:retrieve -m CustomField:Account.B2C_Fiscal_Year__c
sfdx force:source:retrieve -m Layout-"ObjectApiName.Page Layout Name"
eg:sfdx force:source:retrieve -m Layout-"Account.B2C Summer21 Courses"
sfdx force:source:retrieveCompactLayout:ObjectApiName.CompactLayoutApiName
eg:sfdx force:source:retrieve -m CompactLayout:Account.B2C_Summer21_Courses_compact_layout
sfdx force:source:retrieve -m RecordType:ObjectApiName:RecordTypeName
eg:sfdx force:source:retrieve -m RecordType:Account.B2C_Summer21_Courses