i did same job last week (old analog material of about 1 h each) -
* I drew one avi into shotcut,
* drew the sliders on the source-window to the appropriate positions (start/end) (s. pic.)
* and than drew the clip from source-window to timeline.
* Added some filters like "normalize" to increase audiolevel, copied filter and adjustment for later use (paste to next clip)
* and finaly rendered with h.264 (default settings, no change) since my analog material is not so brillant and standard settings for h.264 are a good balance between filesize and quality. (Result is playable by each internetbrowser - suitable f.e.for cloud storage )
Shotcut uses same size and resolution as source
When rendering was ready, I deleted clip from timeline, switched to source-window an drew the sliders for in and out to next wanted part and so on...
...btw ffmpeg is included in shotcut so why worry about commandline switches