What I understand:
Let’s say at 4G end we have default bearer with EPS bearer id 6 drb id 5.
Then after 5g cell added.
Then drb id modify to 6.
So after VoLTE call with new enb and drb id will it impact added 5g cell with drb id 6.
This depends on the features implemented in each vendor but most of them if not all are activating features to prevent the addition of 5G cell while VoLTE call is running and UE has QCI 1 active.
Again this depends on each vendor as there inactivity timers in both 4G and 5G and for some vendors both timers are independent from each other and so if any of the two legs has inactivity timer expired, so this leg should be released and here LTE inactivity timer should be larger than SCG inactivity timer.
While for other cases, both timers are dependent on each other, so the LTE inactivity timer will start after the SCG timer expired.
1- volte call does not allow split bearer so if scg is already added before the call, it will be released. If volte call is setup before endc, B1 meas config will be released
2- both inactivity timers should expire for the endc ue to be released