Those are up-to speeds. You’ll likely get less on average. From my experience, expect as much as 20% slower speeds than advertised on most days.

I personally wouldn’t downgrade to 70Mbps. Maybe if they have an option between, that may be better if you’re trying to reduce monthly costs.

You also may run into upload speed issues as others have said, though that may not change between the two packages you mentioned. With my local ISP(s), you get the same shitty upload speeds for all packages except 1Gbps.

Your mileage may vary.

Then politely tell them that.

PSA: Telling people to “RTFM” is not helpful and just discourages newbies.

If you can’t restrain yourself, then don’t reply. The proper way to handle it is to provide an answer, perhaps even references, then KINDLY advise them on how to find the answers theirself in the future.