Do the free version for a week before buying anything, because it tells you which of your two problems is bigger and that changes what you spend on.
Stack books under the laptop until the screen is at eye height. Work like that for a day, deliberately, even though typing is now awkward. If your neck feels noticeably better by evening, the screen height was your main problem and a keyboard is the purchase that unlocks it. If your neck is the same, something else is going on and a keyboard alone will not fix it.
The same trick works downwards: try a couple of days typing with the laptop flat but sitting on a firm cushion, so your elbows come up to table height. If the wrists settle, the table height was the issue.
What was a waste for me:
- A laptop stand with no separate keyboard. It solves one problem and creates the other, and it is worse than doing nothing.
- A wrist rest, used the way most people use it — resting on it while typing plants your wrists and makes you reach with your fingers. It is for between bursts of typing, not during.
- An expensive ergonomic mouse bought before I had fixed the height. The mouse was never the problem; my shoulder was up because the table was too high.
That is roughly the price of a keyboard saved.