(1) Your wireless is confusing, as you note bridge ports with wlan1 and wlan2 and then bridge-guest with wlan name Guest-Wifi?
Is it a virtual WLAN interface?
(2) Your use of VLAN20 and ether3 is very confusing and you are missing an address for this network and network server etc......
I will assume the following requirements.
a. you need vlan20 on the etherport3.
b. you still wish to have the bridge subnet also available on the port.
If so then the following changes need to be made
...........
/ip dhcp-server
add address-pool=dhcp interface=bridge name=defconf
add address-pool=GuestWifiPool interface=bridge_GuestWifi name=GuestWifi
add address-pool=Voice_pool1 ranges=10.10.20.2-10.10.20.254
/ip address
add address=10.10.20.254/24 interface=ether3-LANVOICE network=10.10.20.0
And get rid of this rule which is wrong on many levels ( you dont tag or untag the vlan you do so to ports (ether or wlan).
/interface bridge vlan
add bridge=bridge tagged=VOICE vlan-ids=20
(3) Trying to make sense of your firewall rules, they are ALL out of order and they are not grouped by chain.
Re-arrange by input chain first with proper order and then forward chain.
(4) You have issues with IP address, you have two IP addresses for WG-Server and one for WG-mobile.
I am assuming you have ONE server for Mt client to MT main router and Second wg for mobile clients to MT main router.
Thus you have one two many IP addresses here...............
Also the nomenclature is awkward, one is for a server and the other is for mobile (implies you name one for the local end and the other for the external end).
Be consistent, call WG server1, WG server2, (both local functions) or WG-ClientMT and WG-Mobile (both external functions).
(5) Confirm, use cases for users from MT client device ( both users and admin) as well as mobile users etc...........
What do they need to access??