Urgent muslin curtain question

[ShouldiWork]

Are they actually functional as curtains - of just poncey window dressing?

We have two massive living room windows. Not really overlooked (trees in the garden - and neighbour behind set at an angle - although I suppose NDN could set up a camping chair and binoculars.

I want a slightly grand 'Beauty and the Beast'-ish. I've priced up velour drapes - they do grand - but £££££ - and look dusty and heavy.

thin curtains are usually see-thru at night when you put lights on indoors in case that makes a difference? They wont keep the cold out if that is an issue as well.

See through like you can see there's a person moving behind them - or see through like you can distinguish the colour of their knickers?

The heat isn't really an issue - it's double glazed in an upstairs room - we've lived a year without any curtains, and rarely even turn on the radiator.

They're completely see through at night.

Yes, completely see through at night, just like nets.