If we understand it correctly, you have replaced the PC original Wireless Adapter for the Intel(R) Dual Band Wireless-AC 7260, correct?
If that is the case, we would like to inform you that Intel does support integration which is when the original wireless adapter is replaced for another one. That is a chance that the adapter installed may not be compatible with the system you installed it in. Please take a look at this only document related to this matter. Intel® Wi-Fi Products — Regulatory Information Regarding Hardware Installation or Upgrade
On our best effort to help you, here as some other documents related to this topic as well as some steps that might improve your experience.
1 - Try to change the channel on the router to a less crowded one.
2 - Disable Power Saving Functions in order to have the adapter working at its maximum performance. - Go to Control Panel >> Hardware and Sound >> Power Option >> Set the High Performance and apply to default settings.
3 - Check the Change Plan Settings: Change Advanced Power Settings >> Power Saving Mode and make sure both On battery and Plugged in are set to Maximum Performance.
4 - Go to Device Manager >> Network Adapters >> Intel(R) Dual Band Wireless-AC 7260, right click on it and select Porperties.
5 - On the Adavanced tab, set the Value of U-APSD support to Disabled.
6 - Cjeck the value of Transmit Power and make sure it is set to 5. Highest.
7 - Set the Preferred Band to Prefer 2.4GHz band.
8 - Set the HT Mode to HT.
9 - Set the 802.11n Channel for 2.4GHz to limit 20MHz
10 - Set the Roaming Aggressiveness to Lowest.
11 - Set the Ad Hoc QoS Mode to WMM Disabled.