Dell XPS 15 9570 i7 8750H - Windows 11 upgraded

It's a 2018 model, so about seven years old.  If the condition and price are both good, within reason it could be a decent system -- make sure the battery has been replaced, preferably within the last couple of years and with an OEM unit -- or budget for a likely need for a new battery within a short period of time.

1. How do you test if the Battery needs replacement? Any OEM brand replacement?

2. Does the KILLER WiFi card come installed?

3. Is upgrading 16GB to 32GB RAM worthwhile?

Thanks

1.  Ask the seller for a battery report, which will show the percentage of the design capacity remaining.

2.  Yes.

3.  Unknown;  you asked this in another thread, but there's no way to answer without knowing what you're planning to run on it.

@ejn63​ 

1. Is the RAM soldered to the motherboard?

2. Better to wait or replace the WiFi card?

1.  No.

2.  Your call.  If you're already looking at upgrades and haven't purchased the system yet, perhaps a newer model with the upgrades you want in place already might be a better option.

I think it might be wiser to consider a business-grade notebook if you're buying used than a consumer-grade model -- Latitude if Dell, or Thinkpad T-series if you're open to other options.  These are generally more robust in construction and better bets for longevity.