Usually, speed tests such as the one you did is recommend to be done when no other application that uses Internet in the background is running.
Checking antivirus and firewall configuration is important as it may impact on the connection as well. If you have any active VPN, please disable it in order to run this test.
Updating the router firmware to the latest version also helps to optimize your experience.
On the adapter, you may want to do the following:
1 - If the Intel® Dual Band Wireless-AC 7260 is native to your system, we recommend that you contact the OEM - Computer Manufacturer Support and check what is the latest driver update they have for the Intel® Dual Band Wireless-AC 7260 and if we understand correctly according to your post you already did it.
2 - As a second option, you can try the latest driver version (18.21.0) found in our Intel® Download Center - On the search bar or our Download Center, just type the model number 7260 in order to being up the options for selection
3 - Make sure to select the driver according to your system architecture (32 or 64 bit)
4 - Once you have installed and saved the new version, go to Control Panel, Programs and Features and Uninstall "Intel® PROSet/Wireless Software", if it is installed. When prompted, choose the option to "Discard settings.
5 - In Control Panel, Device Manager, Network Adapters, right click on the Intel® Dual Band Wireless-AC 7260 and Uninstall it. Make sure you mark the option to "Delete the driver software for this device".
6 - Reboot the PC or scan for hardware changes, check device manager and if an older driver is detected and installed, repeat the actions to uninstall and delete it as well. Repeat this process until the OS does not allow deleting the driver, or until the controller shows as Unknown Device.
7 - Once the steps 4, 5 and 6 are done. Install the new Intel® Wireless driver version (18.21.0). During the first steps of PROSet/Wireless installation, make sure to customize the installation and install all the 3 driver components.
8 - Disable the Power Saving Functions: Got to Control Panel >> Hardware and Sound >> Power Options >> Set the High Performance and apply it to default settings.
9 - Check the Change Plan Settings >> Change Adavanced Power settings >> Wireless Adapter Settings >> Power Saving Mode and make sure both on battery and Plugged in are set to Maximum Performance.
10 - On Control Panel >> Device Manager >> Network Adpaters >> Intel® Dual Band Wireless-AC 7260, right click on it and select Porperties.
11 - Select Advanced Page to set the value of U-APSD support to Disabled.
12 - Check the value of Transmit Power and make sure it is set to 5. Highest.
13 - Set the Preferred band to Prefer 2.4GHz band ( Signal Penetration is better )
14 - Set the HT mode to HT mode for 802.11n compatibility, VHT mode is for 802.11ac compatibility (5GHz band is more sensitive to obstacles).
15 - Set the channel Width for 2.4Ghz to limited 20MHz as it has smaller bandwidth than 40MHz, but it has better penetartion capabilities which improves the connection signal.
16 - Set the value of Romaing Agressiveness to Lowest.
17 - Set the value of Ad Hoc QoS Mode to WMM Disabled.
18 - In order to optimize your connection, find the optimized wireless connection settings between the Wireless Adapter and the router by choosing the settins which suits the network environment and the router, with this donem you may experience better connection quality and more stable connection.
19 - Choose a less crowed channel on the router.
Thanks for incredibly detailed response! I forgot to mention that I had updated to the latest driver provided by the laptop OEM. I changed the driver settings you suggested, but performance is the same.
I've got no control of the paranoidware (aka Security software) that runs on my corporate laptop so I can't disable it. It's highly possible it is the culprit. I just found it odd that the performance was almost exactly half of my Macbook.
Thanks again for your response.