Couple of things I noticed, on the Linksys router I can only set the IPv4 DNS, and enabling this kills IPv6 access. Decided to leave it on default for now and just manually point devices to my pihole instead.
Couldn't work out how to turn off the Wi-Fi either but a quick search pointed to pressing "CA" in the small notes at the bottom to unlock the extra Wi-Fi settings.
Also, definitely worth investing in Wi-Fi 6, doesn't even need to be 6E.
With the Linksys router: 670mb down, 460mb up
With the Unifi 6 Pro: 880mb down, 670mb up
This is testing with a Pixel 6 Pro which granted doesn't have the best Wi-Fi performance so your mileage may vary.
I do believe the 3gb package does come with a Wi-Fi 6 router, 1gb only comes with the older 5.