Does DactNix Arch Linux support my use case?

[fxc]

I would expect it can run 'mplayer'.

I am not familiar with 'mplayer'. According to this video it seems that it can play video files yes, but only in sequential order. I need a fully featured video player that supports pausing, rewinding, jumping to arbitrary points in the video, and raising/lowering the volume.

But you're likely to find the PineTab underpowered if you're used to typical modern x86 systems.

What do you mean by that? Do you mean underpowered as not having as many (software) features? Or underpowered meaning the processor is not as powerful as modern x86 systems? All it needs to do is play videos for me. I've worked with Raspberry Pi before. If it's at least that level, that it's fine. Or underpowered meaning that the electrical power is low? I need the battery to be useable for 6 hours, without a power cord.

You're not limited to Arch.  One of the many nice things about Pine64 products is the wide variety of operating systems.  Currently, ready-to-go images are available for Manjaru (which is also Arch-based), Mobian, pmOS, Sailfish, and UBPorts (which is Ubuntu!).  There are other operating systems you can run on it, but that involves some work.

How much work? And what technical level?
Are there tutorials about how to install other operating systems on it?
The main concern for me is time. If it takes an inordinate amount of time to install another OS on it, particularly if DactNix Arch Linux OS supports my use case, then I will just use it, and not bothering with installing another OS instead.

Those mentioned operating systems are not available on the PineTab2, the user thought you ask about the regular PineTab.

Please do not consider the PineTab2 at this point any further, it hasn't even shipped yet and is in an very early software state, including buggy WiFi, lack of Bluetooth, lack of working cameras and probably a lot more issues.