In addition to having great flexibility over demuxer, decoder, processer, encoder, muxer choice and settings, ffmpeg can crop, stream, merge audio and video from different sources and perform many other tasks.
There are multiple GUI implementations of ffmpeg for ease of use. Among the most commonly used WinFF (Windows, Linux), Avanti (Windows) and Miro (cross-platform) are worth taking a look at.
Among the more common formats ffmpeg can handle are h.264, HEVC(h.265), mp3, AAC, mpeg-4, wmv3, ProRes, QuickTime, SWF, Speex, FLAC, VP9 and many more. To get a full list in terminal type: ffmpeg-formats
Because ffmpeg allows transcoding on the fly and supports multiple streaming protocols such as rtmp, rtsp, http, ftp, hls, you can use it to stream to services such as twitch.tv or set up your own streaming solution.
You can use both local realtime recordings or another stream as a source, transcode it if necessary, and output it to a different stream.
ffmpeg -i rtmp://server/live/originalStream -c:a copy -c:v libx264 -vpre slow -f flv rtmp://server/live/h264Stream
There are presets for everything, so you don't have to delve deep in to advanced features if you don't want or need to. And in most cases you won't have to because the presets are great.
Although HandBrake is pretty straightforward to use, you can adjust pretty much any aspect of your conversion if necessary. For example, when transcoding video you have the option of adjusting between constant and variable framerate, adjusting average bitrate and constant quality, having 2-pass encoding or not, as well as tinkering with encoder specific options, and many, many, many more options.
The GUI makes it easy to encode by providing profiles and a simple GUI, but offers extensive encoding options for people willing to learn and spend time experimenting.
I know that it is not as high quality, but transcoding terabytes of 1080p videos to h265 without hw support isn't realistic and wont be for a long time
VLC can play practically any audio or video file you ask it to and if you're not looking for a dedicated heavy-duty transcoder, but just something that can do it once in a while, you can avoid installing a separate tool by using VLC.
If you want to convert more than one file at a time, you have to use either the command line interface or resort to script writing at which point there is software that does it better.
In addition to having great flexibility over demuxer, decoder, processer, encoder, muxer choice and settings, GStreamer can clip, crop, stream, extract frames, merge audio and video from different sources and perform many other tasks.
Among the more common formats GStreamer can handle are h.264, HEVC(h.265), mp3, AAC, mpeg-4, wmv3, ProRes, QuickTime, SWF, Speex, FLAC, VP9 and it can also be extended with other libraries to support different formats.