Help Needed: USW-Aggregation Addition and Network Topology Optimization

I need some advice regarding my current network setup and planned additions. Below is my existing topology, and I’m considering removing the vent panel and adding a USW-Aggregation switch to offload some of the load from my UDM SE, especially from the U7 Walls and USW-Flex devices. I’m concerned about whether my current backplane of 1 Gbit will struggle with this setup or if I can maintain it. Going forward, I plan to add more hubs, and I’m running out of ports. Do I need a USW-Aggregation switch? What performance upsides or downsides should I expect?

UDM SE - current topology

1. U6 Pro Wall PoE+ (supportive)
2. U6 Pro Wall PoE+ (supportive)
3. USW-Flex PoE++ (garage)
   1. UDM SE
   2. U6 Mesh PoE (outdoor)
   3. G5 Turret PoE (triggers a lot of events)
   4. G5 Turret PoE
   5. G5 Bullet PoE
4. Sonos PoE
5. Hue PoE
6. Fans PoE
7. G5 Bullet PoE
8. G5 Bullet PoE
9. U6 Enterprise PoE+ adapter (main)
10. WAN 1 GB / 1 GB
11. U6 Enterprise PoE+ adapter (main)

Wireless Mesh Uplink

1. Boiler

VLANS

1. Main
2. IoT
3. NoT
4. Guests
5. Surveillance
6. Sonos

Upcoming devices

1. Tado Hub PoE
2. Homey Hub PoE
3. Removal of Wireless Mesh Uplink

UDM SE - future topology

1. Tado PoE
2. Sonos Boost PoE
3. Hue PoE
4. Fans PoE
5. Boiler
6. G5 Bullet PoE
7. G5 Bullet PoE
8. Empty
9. Empty
10. WAN 1 GB / 1 GB
11. USW-Aggregation
    1. UDM SE
    2. U6 Enterprise PoE+ adapter
    3. U6 Enterprise PoE+ adapter
    4. U7 Pro Wall PoE+ adapter
    5. U7 Pro Wall PoE+ adapter
    6. Empty
    7. Empty
    8. USW-Flex PoE++ adapter
       1. USW-Aggregation
       2. U6 Mesh PoE
       3. G5 Turret PoE
       4. G5 Turret PoE
       5. G5 Bullet PoE

Questions:

1. Will the 1 Gbit backplane struggle with my current and planned setup?
2. Should I invest in a USW-Aggregation switch?
3. What performance improvements or issues should I anticipate with this change?

Thanks for your help!