I'd like to get JPGs from https://old.reddit.com/r/lakeporn/top/, https://old.reddit.com/r/Beachporn/top/, https://old.reddit.com/r/BotanicalPorn/ printed, to hang them on my apartment's walls, in the most gigantic print size without any loss of quality.
I don't have a photo printer. So I'll save the pictures to an USB, bring the USB to a photo printer (like Costco), and have Costco print them.
Does it matter what file format I use?
If it does, what format ought I convert the JPGs to?
Any recommendations other than IrfanView for the conversions?