Depends on strength, temperature and how much is pulled early doors, if it's hammered early and has a large headspace the 3/4 days rule is fair, if it is only lightly used early on and has little headspace you can double that time, particularly with 5% plus beers..
Did mine during lockdown. Setup a Angram beer pump, with a line, add a vitop connector and buy the 10L beer in a box from the local breweries. Easy as. Converted a fridge so it acts as both a fridge and fermentation chamber with a temp control as I also brew my own in a Grainfather. You can still us a keg as well on a hand pull beer engine providing you have a non return valve fitted, keep it at a nice low CO2 level. I prefer cask though, none of this fizzy beer.. Probably cost about £150 for the full setup.