For an active survey where the application requires a minimum RF of -73 dBm, the mobile device used for the survey should have a receiver sensitivity of -70 dBm or better. This ensures that the device is sensitive enough to detect the minimum required signal strength for the application to function properly.

In a warehouse setting, the height at which access points are installed can significantly impact the wireless signal. If the access points are placed too high, the signal may not adequately reach the users. Additionally, absorption by materials commonly found in warehouses, such as metal racks and goods, can weaken the wireless signal, negatively affecting the users.
https://www.cisco.com/c/en/us/products/collateral/wireless/aironet-1250-series/design_guide_c07-693245.html#

Changing the TPC Power Threshold to -65 dBm would generally result in a decrease in the transmit power of APs to maintain a smaller cell size. This helps in reducing interference and improving overall network performance. A lower threshold means the APs reduce their power to ensure the signal does not exceed -65 dBm, leading to decreased signal strength at the client side.

When designing anchor redundancy for guest clients with auto-anchor configured on a WLC running version
8.1 or above, setting up Guest Anchor Priority ensures that one anchor is treated as active while another acts as standby rather than load-balancing clients between anchors which is not desired in this case. References := (CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice)

The behavior of guest client sessions in the US being anchored to the WLCs in Europe despite the presence of a local anchor WLC can be explained by the failure and subsequent recovery of the US anchor WLC. During the failure, the guest sessions would have been transferred to the European WLCs. After recovery, if the priority settings were not correctly restored or if the system did not automatically revert back to the local anchor, the sessions would remain anchored to the European WLCs3.
References: CCNP Enterprise Wireless Design ENWLSD 300-425 and Implementation ENWLSI 300-430 Official Cert Guide Premium Edition and Practice.