We currently use the Tag Manager way of loading Google Optimize, but using optimize.js likely has much better performance.

https://support.google.com/optimize/answer/9692472?hl=en

This could be a big improvement for us. From a first look at the lighthouse tests we're adding it seems that whenever analytics and/or gtm is blocking the main thread for a significant amount of time, then the total page score is significantly lower (10 or more out of 100 points down).

UPDATE: I created this ticket a while back when we didn't have as much info on general GTM performance. Likely the problem is more due to other things in GTM firing at about the same time.