Mesh Radio Frequency and Offline Treshold

Hello, I have 2 EW1200 G Pros, and I'm trying to make reliable mesh system in my house
1 router is on first floor and the other on the 2nd floor connected trough AP Mode (Wired Repeater)
My question are :
1. What frequency should I put on both router, should make both have same radio frequency, or different one to another, or just leave it in Auto radio frequency mode?
2. For Offline Treshold, how many -dbm should I put on? Is -85dbm still the recommended option or is it vary based on router location? Because sometimes the connection is not feels like roaming. I have 200Mbps internet speed, and if I move to another spot close to the 2nd router, the internet speed not immediately reach >150Mbps, it starting from slow speed, after few minutes it goes normal to 200Mbps

Thank you in advance

Dear sir

Thank you for contacting Ruijie Suppor team

1. You can keep the channel as Auto, and the device will automatically select the best channel according to the environment when powered on.
2. There is no recommended value for offline threshold, which needs to be configured according to the on-site environment. If the user is disconnected frequently, it is recommended that you reduce the value of offline threshold. It may be that the user has not connected to the new EW during your roaming process, and the user is still connected to the previous AP, so the rate is slow at first. if so , you can increase the increase the value of offline threshold