Also, I found out more about frets. Fretless gives you more range in-between the frets (basically each "fret" will let you access the spectrum between half steps). Yeah you can make fretless sound like fretted if you want but like technically you'd have more range on like, a 5-stringed Cello rather than 4, but there's no need for options you don't use.
and there are disadvantages to fretless like