For the DBL,it is only to check the domain name and RBL is only to check the IPs,but at Xeams,it check the domain and further extract the IP and check RBL too,if IP is in RBL,it return DBL listed.

For example,check from check.spamhaus.org,the subdomain sctrack.sendcloud.net is clean,even it is A record's IP is SBL,it should be been deemed as DBL,as DBL is domain base,not IP base,another example cpt-booking.chunsing-logistics.com is same,domain check is clean.

Is it possible only to check domain on DBL without further check whether it's IP in RBL or not?

For the DBL,it is only to check the domain name and RBL is only to check the IPs,but at Xeams,it checks the domain and further extract the IP and check RBL too,if IP is in RBL,it return DBL listed.

For example,check from check.spamhaus.org,the subdomain sctrack.sendcloud.net is clean,even it's A record's IP is SBL,it SHOULD NOT be been deemed as DBL,as DBL is domain base,not IP base,another example cpt-booking.chunsing-logistics.com is same,domain check is clean.

Is it possible only to check domain on DBL without further check whether it's IP in RBL or not?

The Domain Inspector filter is designed to see if it leads a user to visit a blacklisted site. Therefore, it does both DBL and RBL lookups. Why do you want to do one but not the other?