Prepping Macbook to hand in for repair - Advice

Hello All

I'll be handing in my MacBook to a an iStore (an Apple Premium Reseller here in the UK) to have its keyboard repaired. However, I've been getting a bit anxious about prepping it before handing it in from both a data security and safety point of view.

I was just wondering what people suggest I should do before handing it in? Most stuff I have found online have concentrated on making backups (already done) but not so much on securing your personal data, passwords, login details, access to online accounts, etc. So any advice or checklists anyone would have would be very much appreciated.

So far I've:

1) Done a Time Machine Backup.

2) Manually removed all documents and personal files.

3) Deleted Apple Pay cards.

Mainly looking for ways I can:

1) Remove access to online accounts.

2) Delete saved passwords from only the MacBook (keep access on other Apple devices)

3) Prevent access to Apple Account and Wallet.

4) Anything other precautions advised.