i tried both 3 links and 4 links for rear. I use 4 links so that the backside of the upper links are locked by a long screw and a M3 nut. I pop the Y rear upper link a few times (rear part). Some people put a oversize washer to secure it.
Old Scx10 pre-assembled kit actually had more good stuff than the new kits. At least, the older SCX10 Honcho pre-ass kit had bead-lock wheels. And like yous had the metal 3 links.
My dingo now has four links(rear); i tried both short and long (rear upper plastic links) from the kit to adjust the "pumpkin/rear axle" angle. These things can upgrade too many stuff and really cost $$. Regular trail crawling is OK with plastic. But once if you need a lot of wheel spinning power, then the plastic will flex and may break the drive shaft; especially the 3 links will pop out.