Document best practices to set up large simulations

[kdayday]

From Luke: Document "best practices to set up large simulations (current practice seems to be i iterate a lot with jose about weird kwargs I didn't know about for network and sim setup)"

"the last oen I had trouble understanding was reduce_radial_branches = true... I also don't full understand the area-based vs. line-based constraints/PTDF and seem to always hit infeasible builds if not combined right.."