TRS is a balanced cable so technically you could use a TRS to TRS cable if your speakers have the input option. It's just easier to carry a pigtail adapter so you can just use XLR cables for everything. You can probably just use a Y adapter too for splitting the aux to 2 subs. I use the fancy box because I have it.
I recommend using XLR connectors whenever possible. They're far more robust and have a much more positive surface area contact system. XLRs also have better grip and have less tendency to fall out/pull out. 1/4" sucks for reliability and contact surface area relative to 1/4". 1/4" gets used on a lot of gear because it takes up a lot less real estate compared to XLR and they cost less from a manufacture's standpoint.
