Hi Far!
The '3' is for 3rd gear, so yes, like Supe's 'manu' mode.
Great legroom in the back and we're tall people, the convertible is 4 seats only, but I think the saloon will be 5; you'd need to check.
Yep, there is definate turbo lag, especially compared to the Supe and the T5 seems more 'laggy' than our previous V70 (LPT), but after that initial hesitation, she flies! I'm sure the chip will sort it out! Ours was already lowered when we got her, but we fitted a strut brace pretty quick which helped a lot with the handling, but if you're going for the saloon, I don't think you'll have much of a problem.
Good luck & keep us posted!
Jen