Wi-Fi deployment depends on the environment, type of devices, network traffic, and internet speed. but here are some general guideline that I would recommend:

Fast Roaming: In general fast roaming, which normally is a combination of 802.11r/v/k, helps with having better Wi-Fi experience. For best roaming result, always Run a site survey on both channels (if both are being used) and ensure adequate Wi-Fi overlap.
»»Look for the signal strength between one Access Point and another via MAC address (BSSID), and/or SSID.
»»The best range for roaming functionality between access points is -70 dB to -77 dB.

The only time you may need to disable fast roaming is when you are troubleshooting your network. Most new wireless client devices support fast roaming, and there should be no problem with them. However, time to time there is one device in the network that does not support fast roaming that may or may not result in Wi-Fi issue. Best way to troubleshoot this is to disable fast roaming and try again.

Wi-Fi Calling: First make sure IPSec Passthrough is enabled on the router. This is required so the phone can create a tunnel to the carrier server and start Wi-Fi calling. Next ensure the carrier settings on the phones are up-to-date. Sometime the service providers require an update in the phone setting, specially when there is a major SW update on the phones. If you still have an issue with Wi-Fi calling, try disabling Band Steering as your next troubleshooting steps. In some cases this may help.

One SSID or more? Based on consumer wifi surveys, the best wifi experience is when you connect your devices to the network once and then forget about them. Mostly this is achieved by having one single SSID for the entire network, so users don't need to switch networks. But sometimes you may prefer connecting certain devices to a separate SSID for various reasons such as guest Wi-Fi, connecting wifi cameras, or connecting remote controls. That's when multiple SSIDs are useful.

Hope this helps.