Best practices for conversion tracking

Hi Team.

I have taken over a website and there is many different conversion tracking tags installed.
I believe this is contributing to inaccurate data being received.

What are the best practices to fault find double tags, unnecessary tags whilst also keeping a working system flowing nicely?

Whether that be tracking Conversions with shopify integrations, as now it is recommended to use pixels instead of additional scripts.
Whether that be pulling information from Google Analytics for Google Ads measurments
Or Using Google Ads its self?

Is there a way to have all these activated for continual A/B testing?

Much appreciated