You compared the Session Recording files obtained from PAM Gateway RDP and are bigger than the Session Recording files done by RDP Access, you ask if this is normal behaviour.
PAM 4.2.3
The RDP Gateway recordings are the same as the RDP Proxy Service Recordings, since both are done by the RDP Proxy running on PAM appliance
Session Recording created with PAM Gateway should be similar as the ones taken with RDP Proxy
This is sample of sizes all done with same connection to same target windows server
581K is done from rdp access
2.42M is done from pam rdp proxy
2.33M is done from pam gateway