'Here you are', 'there you go' and 'here you go' (which certainly exists) are used interchangeably in the following contexts:
*By someone working in a café/shop who is giving a customer something they have asked for.
*By someone in a café/shop giving the customer their change (money) at the point of sale.
*By friends and acquaintances giving each other something that has been asked for - this could be an object or a piece of information, like a phone number.
These phrases are used when the speaker wants to be informal and friendly.
'There you go' can also be used in the same way as 'There you go again'
This is used when the speaker wants to express mild criticism of someone for a habit that the speaker finds annoying.
The phrases 'Here we are' and 'Here we go' are often used when the speaker wants to encourage or support someone to do something. 'We' is used instead of 'you' because the speaker wants to show that he/she is helping. For example:
*when the speaker is helping an elderly person do something that is difficult - e.g. get into a car/up some steps
*when the speaker wants a child to do something that the child needs help with - e.g. getting dressed/cleaning teeth/tidying up
These two phrases are also used when the speaker wants to encourage or persuade someone (often elderly, or a small child) to do something that they don't want to do. Because of this, these two phrases are linked to bossy behaviour (the habit of telling people what to do). So even when the speaker is being kind and helpful, using these phrases with 'we' can make the listener feel that they are being treated as a child. A good example is a nurse/doctor encouraging a sick person to do something: For example: Here we go, Mrs XXX, let's just take our tablets' - Most adults would feel annoyed by this.
Interestingly, the phrases with 'we' are not often used when the speaker is actually talking about the 3rd person plural! I've no space to give examples - hope someone else can?