Realistically answering the bridge size would be obviously fitting big cameras on set for dynamic angles/shots. My thought for canon would be the overall design of the bridge was for redundant systems and overall spaciousness. To me that is more personal preference than anything else, it would be like asking why is any bridge on any ship big? A small CIC would be realistically sufficient if we wanted to get into sizing. As for the transporter room they get into why it's so big and that is due to using an inefficient and power hungry means of transporting people that has been phased out of ship design already (basically a past design dud). As for panels on the Shenzhou they have a lot of tactile control surfaces (throttle/joystick) and buttons compared to the JJ-Prise era for sure which is primarily all touch systems. Minus the more TNG film lighting scheme used on set and on camera I'd say they did a fairly good job of advancing the ENT tech look or explaining why something is the way it is on screen. To really hit the mark they should have tried to aim for the more ENT lighting on set for the Shenzhou and thrown out the whole ridiculous holo comms thing which just really doesn't belong in Trek in general.Why is the bridge the size of a football field and equipped with panels that look like the stardrive section bridge on the E-D? Why is the transporter room ridiculously huge with tons of room between each pad? Why do all the panels look more advanced than what's on the JJPrise, which is further in the future than the Shenzou in an alternate universe that had its technology advanced by time travellers?
None of this show fits in the past. It would work perfectly after the TNG era.