Add Solution in data flow after checking condition true in Data flow (power automate)

Hi 

I am new in D365 .

I want to create some function or power app or power automate for sending data to our external third party API in JSON format depend on one of the form condition is true.

So far I have created Dataflow for check condition and have created Solution (still creating plugin) . my question is , how I can add Solution in dataflow ?  like , if condition is true then add solution.

which one is best practice 

1. Do all join query (dataverse) in  Flows and add HTTP in Flows

OR

2. create custom API (Solution & Plugin) and then add them in Flows 

Thanks