Migrating from ASUS RT-AC58U to Linksys WRT3200ACM


I'm relatively new to OpenWRT, but have used things like Tomato for years. Also, apologies if this type of issue has been discussed, but couldn't find anything too similar.

Anyway, roughly a month ago, I installed OpenWrt SNAPSHOT r1834-0f04829 on the ASUS RT-AC58 and everything is working fine. The hardware in this box is a bit limiting, so I bought a Linksys WRT3200ACM to replace it with. I installed OpenWRT 18.06.2 and configured it pretty much the same as I did with the AC58.

Basic Config:

Interfaces: WAN, LAN, TVLAN
Internal WiFi disabled (dedicated AP connected to LAN zone)
TVLAN, LAN --> LAN zone
WAN --> WAN zone
Different subnets/IP ranges LAN, TVLAN
No QOS/SQM installed

When I swapped it out, everything pretty much functioned as expected, with the exception of the streaming services in the house. Youtube TV, Netflix, Amazon all take forever to load and will occasionally warn about slow internet speeds. Speed tests using a computer wired to the port return > 100Mb/s. If I switch the TV or Roku over to WiFi, speeds return to normal and the lag is gone. After installing SQM and trying some of the other ideas mentioned in various forums, I reverted back to the ASUS router and everything is fine again. I'm going line by line in the config files looking for any differences, but have yet to find the smoking gun. Anyone have any thoughts on what could be going on?

Thanks in advance.