They're in 6" pots at the moment. They've grown quite a bit more since that picture. I have one plant in an 8" pot and that's definitely larger than the rest now but it's not possible to come to a conclusion as to whether this has caused it to grow more as it's a different variety than all of the others. The reepers were the slowest but their leaves are so large and getting taller now. Most in 6" pots are still hardly showing any roots out of the bottom.
A couple of mine started growing buds, one of the Reepers (as in that last picture) and the one in the large pot. I've topped most of them now apart from the Reepers which has got rid of the buds and started some new growth. I'm hoping this makes them more bushy while not growing too tall and it's stopped them trying to flower for now (too early?).
First timer so not sure on other questions. 2 per 9" pot sounds alright for now. Putting them outside I think is too early, especially when thinking about keeping them out overnight - probably need at least until May at earliest if not mid-May to June. I'm planning on keeping mine indoors unless they become too big and then maybe a few i'll move outside.
Still struggling to get pots and compost atm. Ordered online but the place is taking ages to deliver which is understandable given the circumstance albeit still a bit frustrating when they only send out a generic email about orders taking a while. That was over a week ago and still nothing.
The final pot size I'll be using is 10" which I believe is around 7.5 litres, assuming I receive them, if not it'll be interesting to see how well they flower and fruit in their current pots. I probably have enough compost to get one into a clay large outdoor pot but also have some dwarf tomatoes on the go so will be difficult to decide who gets promoted

.
Is there an ideal date to get them into their final pots? I assume if you leave it too late they'll start putting out more growth rather than flowering and putting out pods?