As long as you are using a quality lightening cable, then USB connections are always good. I have not com across any other reasons for failure apart from inferior quality cables.
Bluetooth performance issues are nearly always down to phone software. iOS 14 had some bad versions for bluetooth connectivity. Upgrade your software to latest version or try to pair another device to check.
Bluetooth performance issues are nearly always down to phone software. iOS 14 had some bad versions for bluetooth connectivity. Upgrade your software to latest version or try to pair another device to check.