The baby wrap is tied at the height of the waist, the hips, you can also lower it on the buttocks if you want or raise it on the stomach. You don't need to use your legs to tie the knot, everything happens with your upper body. There is no reason why you can't tie the knot sitting down. It is necessary to have a little space between the lower back and the back of the seat during the knot's placement and a little space on the sides. The advantage of the wrap is that you can spread the sides against your body and therefore be able to sit without discomfort due to folds.
Around 4 months, when the baby can open his pelvis, he will embrace you with his legs, so the chair must be a little wide.
Around 6-8 months, he becomes more voluminous in a tummy-to-tummy position and his feet will touch the backrest. The wrap is interesting for the first months of life, when the baby is not too big or too mobile and when you can carry him many times during the day. The fact that you can have the knot on you beforehand and be able to put baby in and out without undoing the knot can be an advantage.
The Sling can also be an interesting way for you when the child grows up. It has the advantage of being quick to put on, but the weight is only on one shoulder.