Hi team, Is it a good practice that have more than 1 feature on 1 page?

Yes. It is rare to have test interaction effects that end up mattering on the outcome. It is much better to have as many tests going at the same time as possible so you learn faster and can improve your product faster. If you have strong suspicion that two tests might interact with each other in a bad way, you can make use of Growthbook's namespaces to serve the two tests to different groups of users.

Thanks. Let say I have 3 features in one page, so there should be 3 experimentI_id and the best practice is put these value into an array or something?

There shouldn't be any need to reference the experiment_id within your code. You only reference the feature flag to see it's value and use that to determine which code to show them. When that happens Growthbook's trackingCallback gets called which has the experiment as part of that and you need to then send a tracking event to your event database with the experimentId.