Netgear R7800 only getting about 140Mbps down - why so slow?

okji, can you tell me your settings in Windows for the WiFi drivers?
I would do the following just to troubleshoot:
In power options in task bar open it and change WiFi power saving to minimum.
In adapter options in network settings, do the following:
Set roaming aggressiveness to Lowest

Lastly the performance difference between my Dell and your Thinkpad could also come down to antenna placement and build differences in our respective laptops which unfortunately we have no control over.

I'm back on Debian. I don't ever use Windows so I want to see if I can get faster on Debian.

Even in Linux you can try to disable power saving and reduce roaming aggressiveness for the WiFi adapter, just to see if that is the cause. Also consider trying hnyman's latest 17.0.1.1 Snapshot build for the R7800.

Hmm. I'm not familiar with this. I've looked around but I don't see anything related to this. Anybody know if Debian/Gnome has any sort of settings like this that I can putz with?

I'm using Gnome and it only connects to the networks I have previously manually asked it to connect to. It doesn't roam or auto-connect to anything unless i have previously set it.

Instructions to disable power savings on Ubuntu/Mint (will work for you too)

Roaming agressiveness, instructions, these may or may not work.

Also are you compiling your own build, using the stock images or using hnyman's build? I would try with hnyman's build, or try compiling using his build environment.

hnyman's builds:

iwconfig is deprecated. (ah, it just wasn't installed). It appears my power management is already off.

sudo iwconfig

wlan0     IEEE 802.11abgn
          Mode:Managed  Frequency:5.5 GHz  Access Point: 
          Bit Rate=270 Mb/s   Tx-Power=15 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=65/70  Signal level=-45 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:77   Missed beacon:0

Anybody got a link to an easy to understand wiki on how to compile my own LEDE build? would doing this give me noticeably better performance or just marginal? I have no idea how to begin with compiling my own.

I don't think you'll get any better performance making your own build vs pre built images unless you are adding any patches.

Use hnyman's build environment or download his firmware as I think he has some extra patches. He gives clear instructions and has build scripts. I posted the link previously. Make sure to use the "make menu config" option to add or remove any packages like Samba, OpenVPN, DLNA via build menu, before you use the "make" option to compile.

Here's the link to the general build instructions though, if you want:
https://lede-project.org/docs/guide-developer/quickstart-build-images

I think you'll do fine, I had no experience with any of this till 2-3 weeks back, the community is fairly helpful, if you run into issues.

hnyman is a developer? This is a version that has recent "fixes" that haven't made it into the current stable release?

He releases snapshot builds every few days for both 17.0.1.1 and master branch so yes, they are up to date. Use the 17.01.1 builds for stability or go for his master branch builds if you want bleeding edge. He tests his builds before releasing them too.

You might test my next master build (coming later today), as it will add the radio calibration fixes from dissent1 that are discussed in LEDE pull request https://github.com/lede-project/source/pull/1153 and originally in forum Netgear R7800 exploration (IPQ8065, QCA9984)