You can look up the actually used settings in the logfile.
Start and stop a recording in simple output mode. Then go to Help→Log files→View current log. Near the bottom there is a section in the logfile from your recording like this:
Code:
16:51:44.128: [jim-nvenc: 'simple_video_recording'] settings:
16:51:44.128: codec: H264
16:51:44.128: rate_control: CQP
16:51:44.128: bitrate: 0
16:51:44.128: cqp: 16
16:51:44.128: keyint: 250
16:51:44.128: preset: p5
16:51:44.128: tuning: hq
16:51:44.128: multipass: qres
16:51:44.128: profile: high
16:51:44.128: width: 2560
16:51:44.128: height: 1440
16:51:44.128: b-frames: 2
16:51:44.128: lookahead: false
16:51:44.128: psycho_aq: true
Notice the "simple_video_recording" info: this means, this section was created by some recording in simple output mode. Might help to identify the correct section if you switch between simple and advanced mode.
Also notice the "jim-nvenc" info: this means, nvenc was used as encoder by my test. If you use a different encoder, you would see it here.
The indented entries are the values you could copy into the corresponding fields in advanced output mode. It may be you see more fields in the log than offered in the advanced config - you can safely ignore these. And "keyint" is given in frames in the log, while it is configured in seconds in the configuration dialog. 250 is the default, which should be entered as 0 (auto) in advanced output mode to also use the default in advanced output mode.
However, to be honest, too much encoder micromanagement isn't good. Since it is possible to record multiple audio tracks in simple output mode as of OBS 29, there is no reason to use advanced output mode any more.