Slow Remote Download Speeds from NAS via Tailscale – Need Help Optimizing Setup

Hi everyone,
I’m having issues with my NAS setup, which I use to allow video editors to access files remotely. I’d really appreciate any help or suggestions.

My setup:

  • NAS: Synology DS1621+ with 3 x 8TB Seagate IronWolf Pro (RAID 5)
  • Router: TP-Link Archer A8 (Gigabit only)
  • Switch: TP-Link TL-SG108E (Gigabit, supports LAG)
  • LAN setup:
    • NAS is connected to the switch using 2x LAN cables with LAG configured.
    • Two PCs are connected to the switch via LAN.
    • One PC is connected directly to the NAS (LAN) and to the router via Wi-Fi.
    • One laptop is connected via Wi-Fi to the router and accesses the NAS remotely.

Remote access setup:

  • I’m using Tailscale to enable remote access to the NAS.
  • I forced peer-to-peer connections using port 41641 (as recommended online).
  • Editors mapped the shared folders via SMB, and connections show as peer-to-peer in Tailscale.

The problem:

  • Local LAN speed is as expected (~100MB/s).
  • Remote download speeds are extremely slow — downloading a 5GB file takes 7 hours.
  • If I bypass the external switch and connect everything directly via the router, it’s slightly better (5GB downloads in ~4 hours), but still far too slow.
  • The peer-to-peer connection seems established, so I’m unsure why the transfer speed is this poor.

What I suspect:

  • It may be due to the upload limitations of my router or ISP, but I’m not sure, on any network speed tests is almost 1GbE download and upload.
  • I’m considering upgrading the router, but my budget is limited.

Upgrade options I’m considering:

  1. ASUS RT-BE92U
  2. ASUS RT-BE86U
  3. Ubiquiti UCG-Fiber (30W) – probably the best, but well over my budget

Questions:

  1. What could be causing such low download speeds even with peer-to-peer set up in Tailscale?
  2. Would upgrading my router improve remote transfer speeds significantly?
  3. Between the router options listed above, which would make the most sense in my situation?