You're getting ready to start advertising your website via Google Ads, you just need to set up conversion tracking so you can see which keywords & dimensions are generating the best results so you can make the proper campaign adjustments to improve performance.
You're just a little confused on one matter:
Should you set up Google Ad conversion tracking directly? Should you set up conversion tracking in Google Analytics and import those into Google Ads? OR should you set up both Google Ad conversion tracking AND Google Analytics conversion tracking, separately?
It can be a little confusing given the options available but option #3 is usually the preferred route. You may already have Google Analytic goals set up and figure it'd be easier just to import them into Google Ads to use as a Google Ad Conversion but I always recommend setting up the Google Ad Conversion Tracking directly if you can. It's going to give you better data to optimize the campaign with. It may seem like there's no difference but there is.
As Google states here "Google Ads performs different calculations of the data than Analytics does, so you will see some differences even when the underlying data is the same."
As a general rule, I use the conversion data provided by the ad platform to optimize ads on THAT platform.
When I want to get the 'bigger picture', I compare multiple different attribution models against each other. You can do this by viewing the model comparison report in Google Analytics.
In GA4 you can see the model comparison here:
This is why you also want conversion/goal tracking set up in Google Analytics in addition to your Google Ads Conversion Tracking.
This FREE 6 Lesson Course Shows You How to Set Up Google Ad Conversion Tracking for Lead Gen Campaigns using Google Tag Manager.