You can try using VLC media player on that PC. That works better than others when using lower end computers. You don't say what CPU is in your computer, and it likely has the standard Intel graphics. Also, if you have an SSD instead of HDD, that will help a little, as well as more DRAM helps with video playback.
In the big picture, if you don't have a 4K TV, and don't have a d 4K screen on your computer, it's a waste to time and SD card space to record in 4K at this time. Down the road that may change.
For now, if all you have is 1080 TV and 1080 computer screen, simply record in 1080. If you're really into editing, and cropping video, 2.7K is an option, but I never use that. I feel it's a waste of SD card space and instead of 9min of video per file you get more like 5min of video per file (correct me if I'm wrong). I already get 3 files per flight using 1080, I really don't want more to deal with during the post edit, but that's just me, I like simplicity. For me 1080 is the sweet spot, clear enough to wow friends and customers, small enough for easy editing. Rarely do I have a customer need 4K for their purposes.
When I get a 4K TV, that's when I'll get a better computer with 4K display and GPU card. Maybe next year. FYI, the new CrystalSky display will be a portable video player too. You can detach it since it's got it's own battery. It's touted to play the unedited SD card 4K video through HDMI out, straight to your TV. If that's true, and it works well, I think a lot of DJI pilots are going to buy 4K TVs very soon....