I just use MPC with good results. They prefer to be potted-on several times, into steadily increasing pot sizes, as they can 'sulk' (stop growing for a period) if planted into too large a pot.
I use 7cm pots then 12cm before they go into their final pot.
A trowel in the hand is worth a thousand lost under a bush.
I suspect they'd be happy in a loam based compost too as I grow my chillies in the soil in the polytunnel which we improve each spring with a good thick layer of home made garden compost and then a generous sprinkle of granular tomato feed at planting time.
I would say JI#2 would be better as it's more free-draining. I forgot to say that I add some perlite if the compost I happen to use seems a bit 'claggy'.
A trowel in the hand is worth a thousand lost under a bush.
If that's what you have they should be fine but 3 for preference as it has more nutrients and mix it with up 4 parts JI with one part MPC for moisture retention.
"We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
Posts
The RHS advises MPC in its info but the key is regular watering and adequate feeding.
https://www.rhs.org.uk/advice/grow-your-own/vegetables/chilli-pepper