Moving to the UK - customs

We will be moving soon to the UK.
What should we expect at the customs?
We have clothing, some (in use) electronics such as laptops, camera, etc.

Does it make a difference if we arrive with everything in our luggage or if we ship it?

When you are arrive at Heathrow, you pass through a custom area. Sometimes you see them standing with a dog and staring at the passengers. They don't check everyone but they stop random people.

Sometimes they just check the passport, ask a couple of questions and let you go. Sometimes they ask you to follow them and open your luggage.

They are looking for tobacco, alcohol, counterfeit items, weapons, illegal animal stuff... etc. but I don't think they care about clothes or used electronics.