If you know dot clock and read line count and refresh rate from OSSC, you’ll get dots per line by the following formula:
dots_per_line = dotclk/(lines*refresh_rate)
That gives your ideal H. samplerate, backporch/active values are secondary and only affect position and/or compatibility. Optimal sampling phase depends on various things and need to be adjusted per PCB.
Dot clock is typically video clock divided by an integer, whereas video clock is usually derived from on-board oscillator / XTAL.