As for flexibility, I figure with any SaaS I have to buy into their product vision as it is inherently going to be a limited/surface area. That being said it gives the benefit of structure and often quicker starts. But given I haven't used both it's hard to have an opinion on a comparison.

As for my port experience. I found the initial quick start really easy and great but then the attempt to test what day 2 would look like a bit harder. For example removing items or updating a fleet of the same item (10s blueprints needing an upgrade) was a faff, understanding the estate of actions I had (which for me was the biggest challenge as that's where all the tricky logic lives) was not intuitive, there were some design decisions where users needed more info about the actions than I want them to (e.g. a namespaces action requires users to know that and pick one despite me having the knowledge to abstract that from them). I also found it very clicky. They have an API but I never sussed how to do declarative setup of port. Plus their API seems to be limited to admin setup of port and doesn't include API request by users (e.g. for use in a CI/CD pipeline or something). I know they are moving quick so some of this may be out of date. But hopefully it's helpful!

Let me look at some helm and then a ping you :-)