You get the the most precise data representing the scene by only enabling Input Profile and White Balance and turn off any module which has either a nonlinear transfer function (Tone Curve, Filmic RGB or Sigmoid), treats parts of the image with different gain factors, e.g. Tone Equalizer or Color Balance RGB or alters color. Adjust the Exposure as needed, it has basically the same effect as changing exposure time, aperture or ISO on the camera. Given that the input profile is correct for the camera and the given illuminant, the pixel data of the image you get this way is the most precise approximation of the true scene color and luminance.
You can try this by taking an image of a color checker: White balance for the Neutral 8 patch and adjust Exposure until the Neutral 5 patch is at L=50.8. If the input profile is good, then you get close to the correct color and luminance for all patches.
Filmic RGB assumes a 12 EV dynamic range by default which is IMO quite reasonable for most sensors. Given exposure is adjusted for 18% average scene illuminance, +4EV for white and -8EV for black are sensible. 100% is +2.47EV relative to 18%, therefore +4EV gives about 1.5EV margin for highlight compression.
If exposure has been adjusted for lower or higher middle gray than 18%, move both sliders by the same amount keeping the 12EV dynamic range between them.
From this starting point, tweak the white / black sliders to massage the highlights and shadows to get them as you like.
Don’t use the pickers but keep the 12EV difference between white and black to avoid this.
Maybe a slider to shift both points by the same amount and/or a “constant dynamic range” option (e.g. shift-click) to pick white and adjust black at the same time so the dynamic range remains constant would be helpful?