Should you always take pre-approved credit cards?

If you open a new account, it will be added to your exiting accounts which brings the average account age down. This temporarily impacts your core as the average age of the credit file is factored into the score. However this drop is usually temporary and always depends how old your file is. If you file is one year old, a new account might lower your score more than it would if your credit file is say 5+ old.
A new account increases your overall credit (and thus decreases credit utilization) and can have many positive impacts. If you have use for the card, go for it.

Then HSBC can also perform a HP, which lowers your score temporarily.

A new credit card will impact your credit score in a few ways.

It will impact the average age of your credit lines, and may drop your score a little. This is not a big deal in the larger scheme of things. It will likely impact your credit utilization ratio (how much credit you use).

Since credit utilization is a huge factor in credit score calculations, this could help significantly if your do not have a lot of credit. The more available credit you have, the easier it is to keep usage under 30 or 10 percent. The lower your credit usage, the better it is your credit score.

There are also long-term benefits of building your credit portfolio. Creditors want to see a demonstrated history of good credit management. Having several credit lines and different products helps build a narrative of credibility. Said another way, someone with a thin credit profile will have a harder time getting a mortgage they want. .