I would put the first two under ‘Hosting and IT Consumables’. They’re fairly generic categories so if you prefer you can add a new nominal account that is more specific.
Costco could certainly go under subscriptions yes.
Either “Subscriptions” or “Hosting & IT Consumables”. Whichever you choose, they’re both P&L overheads so will appear in the same place on your accounts. It’s more for your own reporting purposes, the accountant won’t be too concerned as long as they don’t end up on the balance sheet.
Also if you decide to re-code them later you can now do this in bulk from the ledger detail screen.