From what I understood the original poster was enquiring about a specific series - The Eternal Love 3 (2021) and its prequals The Eternal Love (2017) and The Eternal Love 2 (2018) - wanting to know if they had to watched 1 and 2 first to enjoy 3. For this specific series if feel that it isn't necessary as they can each be enjoyed and understood independently. However, having watched all three, I feel that watching ETL and ETL2 before ETL3 does enhance the enjoyment of TEL3.
When it comes to other series I feel that it is highly dependant on each individual one that you are considering. In general we can say that the more you know/understand the better the enjoyment but in some specific cases it is essential to watch in sequence to understand/enjoy while in other cases it is not.