The voltage produced by a solar panel specified in the datasheet is at 25°C and decreases as temperature rises. I have observed a decrease of around 8% in the maximum power point voltage on hot, sunny days.
If you are designing a constant-voltage MPPT, a good approach would be to take 5% off of room-temperature maximum power point voltage and use that. If you use the room-temperature voltage, the power will drop off quickly as the solar panel voltage decreases due to heating.
If you look at
https://www.pveducation.org/pvcdrom/solar-cell-operation/iv-curve you will see that power drops off rapidly as voltage increases past the maximum power point. Due to temperature changes, it is best to err a little bit to the left of that point to optimize efficiency throughout the day as the panel heats up.
If you want to get every last bit of efficiency out of your panels in all sunlight and temperature conditions, a MCU-controlled regulator is the way to do it. A common algorithm used is "Perturb and Observe". The MCU regularly makes small changes to the voltage setpoint and observes the effect. If the power goes up, it keeps going in that direction. If the power goes down, it goes in the other direction.