All I can offer are my own practices when it comes to picking. You'll have to fit that into what works best for you, for what you intend to use your tomatoes.
I go out every morning and evening to inspect my plants
. I have so many, and all of them seem to have their own agendas for production. I pick them a day or two before peak ripeness because I'm using them for many different purposes and have fruit in all shapes and sizes. The beefsteaks I'll pick just at ripeness or maybe a day before because they're used primarily for BLT and bruschetta sandwiches. Cherries I pick at ripeness for snacks, pizzas, and salads. But paste tomatoes I pick earlier because I need 5 lb or more for sauce batches and I don't want them to be over-ripe for that, if possible. I don't can whole tomatoes so much, though, so even if I do have some over-ripe ones, they all go through the tomato mill anyway, so it's not a disaster.
At the end of the season, before frost can kill the plants
, I pull the vines up with the green tomatoes attached and lay them flat inside the house on a large beach towel to ripen. It's ethylene gas inside the fruit that allows them to ripen without nutrients from the soil and photosynthesis from the leaves, but they'll never be as sweet as those ripened on the intact plant
. Still, for canning, and Fall salads, they can't be beat. We were eating garden tomatoes until American Thanksgiving last year.
PS Daisy, it's a misnomer regarding low/high acid in tomatoes. They all contain the same amount of acid..it's the amount of fruit sugar that varies with variety and ripeness. FYI.