I think those bright colours are for creators of outdoor rooms (or whatever the 'in' term is), not for serious gardeners. Nothing wrong with it if that's what you like.
worth looking at Decaisnea fargesii.
have you any photos showing the top side of the leaves?
They're very slow for the first few years so be patient
I don't know where the advice re airing cupboard came from. Tree paeonies germinate quicker with no heat. Yes, leave them to it. They are hardy. somewhere out of strong sunshine
pot them up in compost and put them outside somewhere.
In fashion atm. Much circulated on social media. Used by those who don't know (or don't care) about micro-organisms in the soil
I find seeds don't rot away in the weather.
If they are ripe/mature they will dry out and be fine. If they are not ripe, they will not ripen once removed from the plant.
i wouldn't remove, I'd be watching most carefully. Very interesting