Bandwidth should not be a problem. The higher your ping gets the more stale shares you get. From traffic perspective the miner dose not have that much. Only takes a block (2mb) every 10min + some back and forth conformation on hashrate.

Not sure what Q/P ratio means but obvious the newer the miner the more btc you get per power consumed.

On older miners you get more hashrate per $. (With lower efficiency obvious)

Prices will be dependent most Lilly on the location you want to buy.

For me it’s like

s9 with 14Th per 1kWh @ 160€

S19 with 110Th per 3kWh @ 1500€