Yeah you hit it right on the money. PPTP ecapsulates/encryptes PPP traffic, and L2TP only ecapsulates. You need IPSec to encrypt L2TP traffic, but you'd only do that if you were needing to send data through PSTN links, otherwise just use IPSec and save the L2TP overhead.
Jan 22, 2019 PPTP vs. L2TP vs. OpenVPN: which one to use Even if it is a bit harder to setup than traditional PPTP or L2TP/IPsec, we recommend using OpenVPN if reliability and security are your main concerns. For best speeds, it's likely that L2TP/IPSec would be faster if you have a very fast broadband connection (over 100 Mbps) - but it depends on many factors. VPN Protocols Compared - PPTP vs L2TP vs OpenVPN vs SSTP Apr 05, 2012 MikroTik VPN Comparison – RFC Apr 08, 2015
Jun 28, 2018
IKEv2 vs IKEv1 vs OpenVPN® (TLS) vs L2TP/IPsec vs PPTP May 14, 2018 PPP vs PPTP — TechExams Community
VPN Protocols Explained - PPTP vs L2TP vs SSTP vs OpenVPN
Aug 13, 2019 Why The PPTP VPN Protocol Is Not Secure? PPTP vs. IPSec. PPTP and IPSec share some similarities. For example, they both use encapsulation technologies. However, IPSec is a whole lot more secure. PPTP is a lot more stable than IPsec. However, PPTP is a lot easier to block with the firewall. IPSec has the ability to encrypt traffic in a way that the end application is not aware of the Is SSL VPN better than PPTP VPN? - Quora