Perhaps surprisingly I've found JQ's 787s have been in reasonably good condition. All still relatively new of course, but a couple of years older than the Qantas examples. They've presumably had a slightly tougher life too! The only issue was with the window dimmer buttons, so perhaps the quality...

With SQ your best bet is sticking with A350s, 77Ws and A388s for PE. Not quite sure if all the 77Ws and A388s have PE but all the A350s do. SQ 256 from BNE-SIN is the only flight with the A350 and PE, so that's probably the best place to start!