The short answer is don’t print layer height 20um on MSLA printers and not just larger ones like Phenom. Stick with 50um. It is the best combination for resolution, speed, and print success rate.
The longer answer is that the 20um is the layer height and is a lousy indicator for resolution. Layer height affects o resolution on Z-axis but could have adverse effects on x/y resolution, which is determined by resin and panel. By printing at 20um, the effect of crosscuring (UV light curing previous layers while printing current layer) is much higher than at 50um, and that lowers x/y resolution. Also, your print time is increased by at least 70% as the exposure time does not reduce linearly with the reduction in the layer height. It is often a loss/loss proposition. Additionally, many resins do not resolve well under 30um, so you are unlikely to gain anything there. There is a reason why we only showed a 50um profile.
Some pros do make 70um or 80um profiles to speed up printing without losing much on z-resolution.
And your exposure time for initial layers is likely way off for 20um (too much time).