Hi there Max,
-My Weller WES 51 station has the default medium size chisel tip. What size tip do y'all recommend?
As Doc said, the standard tip is perfectly fine. It really comes down to preference. I prefer conical tips, which is what I started with on a Weller pencil iron.
-Do you use any helping hands station to put your parts on while working on them? I was thinking of getting something like QuadHands Deluxe WorkBench form Amazon (sorry, not allowed to post outside links)
I have a few of the fancier helping hands devices and prefer the Quadhands by a longshot, but I mostly use it for cables. I've populated more PCBs than I care to remember and I actually just prefer soldering directly on a flat mat on the desk most of the time. The Quadhands investment makes sense if you plan on using it quite a bit, or the lower cost Panavise clones or generic helping hands work great if you don't want to spend $45.
-Are there any modifications available where the RCA and power wires of the Eros 2 come out the back rather than the top?
Sure, your imagination is the limit. Some members have drilled out the back piece of wood and mounted a metal sheet, then mounted the RCAs. You could also use FR4 or phenolic. I personally would just use a forstner bit to drill out the wood partially from the back, then drill smaller holes for the RCAs... or use the "D" sized Neutrik or Amphenol RCAs and drill larger holes for them.
-Any agreement as far as a good soldering removal tool?
The generic $7 jobs on Amazon / Ebay work great. I've spent far more and there really isn't much of a difference.