Isolation temptations

Hi all, just thought I'd introduce myself. I'm a Sydney based casual builder who has been drifting to smaller and smaller builds over time.

I'm at a crossroads with my current rig and am starting the plan to either upgrade or build new.

My Case journey to date:
-Antec 900 (first build ~2010)
-Bitfenix Prodigy (for GF 2014)
-Phanteks Evolv ITX (current rig 2017)
-Fractal Design Define Mini C TG (Wii emulator 2018)
-Silverstone SG11 (Spare parts 2019)
-Golden Field N2S (GF's rehomed 2019)

Looking to go smaller but also torn with mATX vs mITX boards.

Apologies in advance for the silly questions to come.