Migrating to Google Analytics 4 from Google Universal Analytics

With just about a year left before UA goes away, I suppose its time for me to migrate my sites so that I can build up a years worth of data.

For context I manage about a dozen or so sites some public facing, some behind an authentication wall and some which are mainly internal company tools. Most of the sites I manage don’t sell anything or participate in any marketing/email/ad campaigns.

My sites use of GA is very basic, I mainly get asked about pageviews, what pages are popular and traffic patterns. I don’t have any custom events or on page actions to worry about.

Ideally I’d like to keep the current UA tag so that my years of historical data continues to get fresh data added while we fully transition away. I also secretly suspect that the UA deadline will be extended.

In setting up the new property I’m given the option of adding a new analytics code to the head tag of my site or I can apparently use my existing tag and link the old and new property in the background.

My intuition says I should just add the new code/tag and in a year or so remove the original UA tag rather than rely on the backend integration between the properties. I suspect this would have some minor performance penalty / affect my lighthouse score, but in the grand scheme I’m not worried about it.

Has anyone gone through this? Any issues running both side by side? General feelings about the new GA4 tool? I haven’t heard great things, but its been awhile since I last looked into it.