I have a Raspberry Pi 4 smoothly outputting 1080p video via Kodi better than my retired Mac mini 2010. Since my TV is only 1080p I have not tried 4K.
Most my video content is 8000kbps HEVC, 1920x1080 resolution.
I tried using an iPad, iPod touch, and iPhone but none of those natively support alternate containers like an MKV file. Thus, I would end up having to transcode the content to MP4/m4v. The RPi4 allows me to playback this content without the transcoding.