Bluetooth issues (Keyboard / sound); keyboard suggestion

Hi!
I use Anker Ultra Compact BT keyboard with my Mac Pro (10.13.3).

There are 2 issues so far with the keyboard:
When login screen appears I can not enter my password immediately. I have to press random keys for some time until I can start typing anything. Any ideas on how to speed up the connection?

I can not get any boot options to work from the keyboard...Has anybody got this working with their Mac, and this specific keyboard?

Which BT keyboard connects fast enough to be able to use boot combinations? Any specific fail/success stories?

When BT Mouse and keyboard is connected - BT sound to BT2.0 receiver device is choppy. Any advices (beside changing WiFi channels). BT Explorer has plenty of settings - Has anybody tried to play aroynd with those?

Tried switching to USB4.0 CSR module - same issues.

BT module in MP is 2.1 EDR. It will be upgraded to 4.1 via internal adapter. Could this help potentially?

 

Are boot options functional with wireless Apple Magic keyboard?