Comparing data types of a primary and foreign key
I am sure this can be optimized but here is to experiment,

with parent as (select --+ no_merge(dc) no_merge(dccr) no_merge(dtcr) 
distinct dc.r_owner ref_owner,  dc.r_constraint_name,dtcr.column_name
,case when dtcr.NULLABLE = 'N' then 'NOT NULL ' end ||
  case when dtcr.DATA_TYPE in ('CHAR','VARCHAR2') then dtcr.DATA_TYPE || ' (' || dtcr.DATA_LENGTH || ')' 
     when dtcr.DATA_TYPE = 'DATE' then 'DATE' 
     when dtcr.DATA_TYPE = 'TIMESTAMP' then 'TIMESTAMP (' || dtcr.DATA_SCALE || ')' 
     when dtcr.DATA_TYPE = 'NUMBER' and dtcr.DATA_PRECISION is null then 'NUMBER'
     when dtcr.DATA_TYPE = 'NUMBER' and dtcr.DATA_PRECISION is not null then 'NUMBER (' || dtcr.DATA_PRECISION ||',' || NVL(dtcr.DATA_SCALE,'0') || ')'
end c_dt
from dba_constraints dc
join dba_cons_columns dccr on (dccr.owner = dc.r_owner and dccr.constraint_name = dc.r_constraint_name)
join dba_tab_columns dtcr  on (dccr.owner = dtcr.owner and dccr.column_name = dtcr.column_name and dccr.table_name = dtcr.table_name)
where dc.constraint_type = 'R' and dc.r_owner = 'SCHEMA_OWNER')
,child as (select --+ no_merge(dc) no_merge(dccr) no_merge(dtcr) 
distinct dc.owner ref_owner,  dc.constraint_name, dc.r_constraint_name, dtcr.column_name, dtcr.table_name
,case when dtcr.NULLABLE = 'N' then 'NOT NULL ' end ||
  case when dtcr.DATA_TYPE in ('CHAR','VARCHAR2') then dtcr.DATA_TYPE || ' (' || dtcr.DATA_LENGTH || ')' 
     when dtcr.DATA_TYPE = 'DATE' then 'DATE' 
     when dtcr.DATA_TYPE = 'TIMESTAMP' then 'TIMESTAMP (' || dtcr.DATA_SCALE || ')' 
     when dtcr.DATA_TYPE = 'NUMBER' and dtcr.DATA_PRECISION is null then 'NUMBER'
     when dtcr.DATA_TYPE = 'NUMBER' and dtcr.DATA_PRECISION is not null then 'NUMBER (' || dtcr.DATA_PRECISION ||',' || NVL(dtcr.DATA_SCALE,'0') || ')'
end c_dt
from dba_constraints dc
join dba_cons_columns dccr on (dccr.owner = dc.owner and dccr.constraint_name = dc.constraint_name)
join dba_tab_columns dtcr  on (dccr.owner = dtcr.owner and dccr.column_name = dtcr.column_name and dccr.table_name = dtcr.table_name)
where dc.constraint_type = 'R' )
select parent.ref_owner, parent.r_constraint_name ref_constraint, parent.column_name ref_col, parent.c_dt parent_col_datatype
,child.ref_owner child_owner, child.table_name child_table, child.r_constraint_name child_constraint, child.column_name child_col, child.c_dt child_col_datatype
from parent join child on (parent.r_constraint_name = child.r_constraint_name) order by 1,2,3;