Single CF Grow COB LED (300 W) sufficient for one plant?

It should be fine. But you don't have a cupboard or something to put it in? I grew a plant with 160w cfl bulbs in a closet with no extraction but a small blowing fan. The problem you have here is that the light gets lost in the room and doesn't bounce back on to the plant. You will have to keep her moist and humid 60/70%rh recommended at this stage and between 22-28c .

suggestion you need a closet or little tent depending on what you looking for big yield or just for your self they have different sizes that fits your needs keeping the plant out like that doesn't have the environment that it need to sustain keep in mind humidity temperature is a big factor when growing cannabis even if it's for your self you put in hard work just to get something that's not worth it do a little research 😉 I promise you it's not hard as it seem 💯 I'm always open for more questions because I am learning my self and happy to share what I'm learning with others happy growing 🤘

Hello, I think the set up idea should possibly work, my one suggestion would be to surround the area with something white. Like a white plastic tub, it will help to reflect the light versus being drowned out and soaked up by the curtains and the chair. And you may want to move the light closer at some point but watch for the plant to stretch if it does bring the light closer.