Typically, the low speed fans will turn on around 212 and high is 226.
In all three of my vehicles, I use a 180* t-stat in the summer. It keeps the engine/engine bay a tad cooler, winter time, 195.
You can trick your PCM to turn your fans on by disconnecting the coolant temp sensor connector. The PCM will command the fans to turn on LOW. This is a built in safety feature should the PCM not see an engine temp.
On your original issue, it seems as if your cooling system is operating fine. Increase/decrease in the temp gauge is normal. Normally, you don't see this in the winter time.
And I wouldn't trust the temp gauge, they tend to be a few degrees off.
1997 Pontiac Bonneville SEi-SCRAPYARD
2000 Chevrolet Blazer LT 4X4 4.3L
2002 Chevrolet *-10 LS Ext Cab 4X4 5.7 V8