Since I have a colorimeter I try to get the brightness as close to 100 nit as I can. I don't remember what brightness setting that is for my 2 monitors and really that is very model specific.
I never touch the contrast control on an LCD since anything other than the default setting is going to clip the signal so it's best to leave it alone.
HDR the content should be controlling the brightness, your monitor should be locking you out of those controls when in HDR mode.
The only thing I do for HDR is turn down Windows SDR brightness control so SDR white is around 100 nits. After doing that I actually can't tell when HDR mode is on unless I'm viewing HDR content.