Would it be possible to directly connect 2 adjacent factory's (ones that are not separated by a tile). Basically now I can use a chest connection to pretty quickly connect 2, but was thinking it'd be more efficient if I could place 2 right next to eachother and have them connect directly.

That would be possible, but very hard to implement, and it really isn't worth the effort. Is 1 tile in between not space saving enough already?

Nah, not really a space thing. Mostly a "hey it'd be pretty thing". Never know until you ask if it's something that is simple vs something that is hard. (80/20 rule)

Thanks for responding!

I like using a shared chest in between the two factories. Very simple and with high level bots its a great throughput.