Just did the trip SQ8111 SIN-PER on a chartered SQ A330. Despite what the check in person said (and the lounge invitation printed on the BP), we tried but were denied lounge entry as expected. Luggage is as per Scoot, not SQ allowance. We booked Scoot Biz so got the run of the empty J section (there were 3 other people besides us). It was nice to have lie flat seats, but the meal was standard Scoot nasi-lemak with a plastic cup of water. IFE was turned on in J (can't speak for econ), but we would have had complimentary access in Scoot Biz anyway.

So all in all, expect what you'd normally get with Scoot (no more/no less) and the hard product is a nice bonus.