Setting Root Bridge

I have several questions in regards to setting the root bridge priority properly.  We have a our corp HQ office that is running a ex4200VC at the core.  We have 15 addition IDF switches in our building. My topology for each IDF is 2GB LACP fiber LAG's connecting all IDF switches from all floors in all buildings back to our core switch. All switches are Juniper either EX2200 or EX4200. No routers or firewalls between any of them. i noticed when looking at our switches that when i ran the command below on the core my root ID was not for the core switch.

root@MDF1-SW1-EB1F> show spanning-tree bridge

STP bridge parameters

Context ID                          : 0

Enabled protocol                    : RSTP

  Root ID                           : 28672.b8:e9:37:04:5a:84

  Root cost                         : 210000

  Root port                         : ae5.0

  Hello time                        : 2 seconds

  Maximum age                       : 6 seconds

  Forward delay                     : 4 seconds

  Message age                       : 2

  Number of topology changes        : 10645

  Time since last topology change   : 592 seconds

  Topology change initiator         : ae5.0

  Topology change last recvd. from  : 84:18:88:a8:cb:83

  Local parameters

    Bridge ID                       : 32768.5c:5e:ab:66:a2:01

    Extended system ID              : 0

    Internal instance ID            : 0

upon further investigating it was determined that a sonos boost wireless extender on our network is acting as the root bridge.  We have the sonos speakers and boost on our network for different design studios.  currently i have about 20 speakers total spread throughout three buildngs.  That number is going to grow some more here.  We were having a slow speed issue in one area of our LAN.  after months of troubleshooting, testing computers, network, network cabling, speakers, printing, phones, switches, it was deteremined that we had some significan signal loss with our 1gb fiber trunks.  in that area we had 4 sonos speakers, but removed them during the troubleshooting phase. one thing we noticed when they were connecting using the ethernet wire was that you could only connect 2 speakers. if you tried to connect three it would cause the music to be glitchy and not work.

So i am trying to setup all of my switches to play nice with the sonos and vice versa to make the network work properly. 

1. By setting the bridge priority to 0 on the core will that be disruptive at all to the network? will that also require a reboot to take affect, or does the negotiation notice the change after commit and adjust accordingly?
2. Is it best practice to leave all other remaining IDF switches at their default value 32,768 or should i also set maybe one additional one at 4096 so if the core goes down that one will be elected as root bridge in the interim?
3. Because i have multiple VLANS (21 currently) on the network i saw there are several ways to set the bridge-priority based on the Juniper KB article below and what protocol to assign it on. Unless i am not seeing, thinking, or understandingsomething, i would want my core switch for all vlans to always be the root bridge, or is there some reason not to? My topology has 2GB LACP LAG's connecting all IDF switches from all floors in all buildings back to our core switch. All switches are Juniper either EX2200 or EX4200. No routers or firewalls between any of them.
4. will set the sonos boost bridge id to a higher value as well.
5. Has anyone else had to configure Sonos speakers on their network. Are there any other changes that need to be made at the core/MDF, IDF, or interface level to make them all work besides the root bridge

Since i have RSTP enabled based on the output above would i navigate to

#edit protocols rstp

[edit protocols rstp]#set bridge-priority 0

or would i do it a the STP protocol?

Juniper KB article

https://www.juniper.net/documentation/en_US/junos12.3/topics/reference/configuration-statement/bridge-priority-spanning-trees-ex-series.html

bridge-priority (Spanning Trees)

Syntax

bridge-priority priority;

Hierarchy Level

[edit protocols mstp],

[edit protocols mstp msti msti-id],

[edit protocols rstp],

[edit protocols stp],

[edit protocols vstp vlan vlan-id]

Release Information

Statement introduced in Junos OS Release 9.0 for EX Series switches.

Statement updated in Junos OS Release 9.4 for EX Series switches to add VSTP support.

Description

Configure the bridge priority. The bridge priority determines which bridge is elected as the root bridge. If two bridges have the same path cost to the root bridge, the bridge priority determines which bridge becomes the designated bridge for a LAN segment.

Default

32,768

Options

priority—Bridge priority. It can be set only in increments of 4096.

Range: 0 through 61,440

Default: 32,768

Required Privilege Level

routing—To view this statement in the configuration.

routing-control—To add this statement to the configuration.