9105 is AX certified AP(Wifi60 and 1850 is Wave2(Wifi5) , therefor I strongly recommend that you have 2 types of client devices for testing.
1. Run the complete test using Wifi6 client/s connecting to both AP's.
2. Again run the complete test cases using Wifi5 (11AC) client/s connecting to both AP's.
For throughput testing you can use either of the below tools;
1. iperf
2. TamoSoft Throughput Test
I recommend the first option as it allows you to customize the traffic profile (TCP,UDP, number of streams etc.) Always have the server side connected to the switching infra via cable. Then as per your requirement first define the test cases that you are going to run and then run the test as per the above guidelines. I would also recommend that you have multiple clients connected at the same time as this will give more realistic results, and also to use the RF profile which you are planning to use in the real world (data rates enabled, channel width etc.) If real world traffic profile has multicast, make sure to check that as well. (you can use VLC)
When doing the test please record the RF parameters as well (MCS rate, radio connected, RSSI levels etc.
This information here is very highlevel, you will have to customize and choose what you are going to test and not.
