you can use any ESC, for scale crawling, any ESC with reverse is OK but sure will lack of drag brake function or drag brake function is so weak that cant hold the crawler still on hill. I am using Traxxas water proof esc. Buy RTR you ready to go. But you MUST have reverse function. Any ? just ask.
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.