Appointment

You do not need an appointment if it is just to buy something but you still need a Genius Bar appointment for service. They will check your temperature outside the store, go over the checklist of questions, and then have you tell an Apple employee what you are there for. If you know what it is you want to buy and you are not doing a trade in they will offer to have an employee bring it outside and then sell it to you. It that is not the case depending on how many are there you will stand in line outside, then stand in line inside until an Apple employee is available for you.

It took about and hour and 45 minutes when I purchased an iPhone SE 2nd Generation but I was doing a trade in. Patience is a virtue when you go.

You will need to check with the store you intend to visit. It will depend on the local rules re. social distancing etc.