1. the input data, which keyboard and mice transmit is much smaller than audio data. this makes difference to encoding delay. due to its size, audio data needs to be encoded following codec's specifications. AAC takes generally 60ms to encode, and LDAC takes 30ms.
2. if your audio device has ANC, it takes even more delay to process audio data. and if your audio device is two separate stereo earbuds, it requires additional delay to sync sound each other.
3. unlike in ear earbuds or headphones, Keyboard and Mices have enough space to put much larger antenna, much larger battery. it enables much stronger signal connections, so manufacturer can greatly shorten packet retransmission delay.

bluetooth keyboards do have latency. generally below 50ms, which is hard to feel for most users. but some competitive gamers still feel latency and prefer wired one.

Fortunately, Bluetooth LE Audio - Completely made from ground up, solves several problems that Bluetooth Classic Audio has. using LC3 - new default codec for LE Audio like SBC - is expected to be able to achieve 80ms - 150ms delay while transmitting 16bit/48kHz audio.

Unfortunately, No.

Unlike wired connections, in wireless world - audio data needs to be cut into small segments called 'packet' to efficiently communicate with multiple devices, multiple tracks, and more. It even send the same packet multiple times to counter signal loss! And those packets need to be reassembled into an actual sound signal we can hear.

Every process like these require some time, and it would need some serious technological breakthrough to eliminate the delay while maintaining good audio quality.