The settings are different, one is in the workplace, the other is in high school.
But the plots are all about the female lead using a mysterious APP to help her colleagues/classmates and herself, falling in love with the male lead in the process.
These dramas have very little 'drama', they are really light, short and funny to watch~

Both dramas are light dramas, there's not much angst
Both female leads are cooking prodigy, and of course we get to see A LOT of cooking and food, up close and in slow motion

Both dramas feel similar, in concept, the way they were shot and produced (documentary-like).

The Producers tried to focus more on the "the behind the scenes" aspect of producing a tv-show, while Our Beloved Summer focused more on how to film a documentary about random people, and of course mainly the romantic relationship between the leads (which is way more interesting in OBS)
In both dramas there's an idol whose sole purpose is the same (even though they have opposite tempers), to show us some hardships of an idol life : no friends, no real free time, dealing with fans and anti-fans, no privacy... AND to have their first impossible and one-sided crush on the ML !
If you liked The Producers, you'll probably enjoy Our Beloved Summer, I don't know about the other way around

Both are short web-dramas about a relationship where a guy falls in love at first sight with a girl in high school, and he tries to chase after her.
It's short but well-done, it's about falling in love, and growing up, and everything that entails from high school to work life.

Both dramas are coming of age stories with everything that entails : high school drama, sweet first love, strict parents...
ML is also a transferred student, misunderstood because he doesn't "fit in"
But in Forever Love the romance goes further and we actually get to see the life of the characters after high school, university, work...

Both dramas are coming of age stories with everything that entails : high school drama, first love, strict parents...
Main difference is in Our Secret we get to see the life & the actual romance of the characters after high school, university, work...

Both dramas are about cat shifters, working in a bar and living with a human.
If you want a funny, short and easy to watch web drama about cats, then this is for you :)