Please don't go about telling people to try out configs without mentioning what changes you have made and how you have got it to work. It will help the community more if we have a diagnosis for the error.
I have been using the same card since Mojave with both Wifi & Bluetooth enabled continuously and faced no issues with speed. Try removing the Bluetooth kexts and installing them again. Also, see that they are in the right order in the config file.
1) Search for a guide. Maybe like this. Although I wouldn't recommend moving back to clover. There is a good reason why everyone uses opencore. Clover too is using the opencore bootloader and has become a hybrid mess.
2) I'm not aware of the background, but the icons can be changed. A simple...
If you are using the default bluetooth, you need this kext: https://github.com/OpenIntelWireless/IntelBluetoothFirmware
The kexts I have included are for Broadcom wireless cards. The SMBIOS error is because this system is not a Coffee Lake Desktop, it is a Kaby Lake Laptop. A little reading goes...
It's not perfect at all. You can see the errors under the PlatformInfo. What Bluetooth device are you using?
Check what the config should look like here: https://opencore.slowgeek.com/?file=laptopkabylake0635fsPBJ&rs=laptopkabylake063
You may have to re-order your kexts.