My Asus router is running dd-wrt
Personally have enjoyed using DD-WRT for many many years. That said today using OpenWRT which is always updated.
I have a tiny 1" X 2"OpenWRT micro router inside of my Alarm panel that I utilize mostly to measure traffic to and from the combo automation / security panel. Another micro router is a configured as a TOR (Onionskin) wireless router.
I would suggest upgrading your hardware router to something a bit more robust and using opensource software like
PFSense.
Hardware utilized today is a mini PC with 6 Intel Gb ports. Using 2 Wan ports (failover) and 4 Lan ports.
I utilize IPSec clients on my phone (easy peasey to set up on iOS or Android, tablets or laptops (Windows or Linux). No open ports these days accessing CCTV, Automation and security remotely via IPSec VPN.
VPN Speeds are mostly related to what ISP tier of service I have up or down and
bufferbloat.