i guess its assumed that you got enough good torrents so that upload is at max speed.
in most cases, all
leechers want the whole file, but there might be too many
seeders..
usually, for home PC, 'connectable' means that you forwarded ports correctly (NAT) and your provider hasn't put you behind CGNAT.
dunno about
seedbox, but, given their function, ports should be 'open' so they should be connectable.