I airbrush almost exclusively Tamiya paints and find they’re extremely forgiving. I tend to go for a 50/50 mix at about 18 PSI through a 0.3 needle and never had any problems. That’s using the x20 thinner as well. Many suggest Tamiya’s lacquer thinner as even better.
I’ve not noticed the 50/50 mix is particularly translucent and rarely have to worry with dedicated primer, just use a black/dark grey Tamiya as a shadow coat. That said like any manufacturers coverage does vary a little between colours.
Never had a coat that isn’t durable. I’ve noticed on the odd occasion accidentally set air pressures haven’t seemed to make much difference at least for base coats.
Given their ease I would suggest working back from a 50/50 mix to gain the opacity you’re after, maybe 60/40?