2 asus routers and VPN?

[byyuan]

I am using Astrill, and since it works only with certain routers, in my case, AX56U. I bought a second router TUF AX3000 for better wireless connection (5400M???). When I purchased it, I didn't realize TUF AX3000 is different from RT AX3000 (or AX58U). So long story short, I cannot merlin the TUF AX3000 (but would be great if i could!)
Now, I'm using AX56U to connect to internet and run Astrill, then LAN to TUF-AX3000 for wireless coverage. and under TUF-AX3000, I've got my Synology NAS. What I wanted is:
1. Astrill coverage for my home wifi
2. Internet remote access to my Synology
My current setup: Internet-AX56U-TUF AX3000-NAS, with AX56U setup as IPSEC server. I'm able to remotely connect to AX56U via IPSEC, but I cannot get connected to my NAS. Could someone please help me out on how do i solve this?

Thank you!

 

[byyuan]

-----Update--------
It didn't work out in the end. Returning the TUF AX3000. and now using AX56U (V1).
It still has a conflict between Astrill and IPSEC server. When the VPN server is active, Astrill would stop working after hardware restart (auto reboot). Astrill had me a manual solution to SSH to the router, and execute modprobe tun before connecting, and it worked. What's modprobe?? can this be automated with Merlin?