Most if not all of these interior fly throughs that you are seeing on Youtube are done with FPV drones and a pilot wearing
goggles. The smaller drones have GoPros on them and the footage is stabilized in post.
Sure, with some practice you could fly your Mini in a warehouse and do some simple moves, but if you want to be able to progress and get some real dynamic shots, I would get an FPV drone and great googles. There are many small CineWhoops that come prebuilt, or you could build yourself, I have, and mount a GoPro or other action camera on it. It's quite a learning curve with all of the settings to try and adjust for the smoothest flying. Or you could just buy a DJI
Avata, that's what I would do. DJI has one of the best video transmission systems and the best
goggles. I've flown it and it is amazingly easy. You would still benefit from practicing on the simulator first. I believe the basic package comes with the motion controller which is simple to use, but I think you'd want to get the RC with sticks for finer control. DJI sells Refurb drones that are good as new.
Check this out