hey, I have a quick question - is it possible to use Optimizely for experiment set up and tracking and then use GrowthBook only for the analysis part? Does it make sense?

You can use Growthbook for analysis only as long as it can access your datasource. I'm not sure with Optimizely or your set up where your data lives, but if it is one of the datasources here: https://docs.growthbook.io/warehouses then you can use GB. You will probably have a better experience though if you also use GB for experiment set up.