From my personal experience, clients never look at my live portfolio. It is not so easy to find honestly.
Delivery before the deadline is fast delivery and as such SHOULD BE PAID IN UPSELLING.
Rushing a client is unprofessional and micromanaging.
It is very complex discussion. Some reviews weight more than the other, if I have a gig with basic started from 400$ , clients expect a lot more then a client paying 5$, so it depends of the gig.
My advice is to look good at the sample to see if their work matches your need. Just the other day there was a buyer complaining that the quality of the logo is not good, I am not a logo design but as it turns out the quality was fine, just the seller had a style that the clients didn’t want and this could have been avoided by taking a good look at the portfolio.