This property is significantly better than the Signature, although not strictly a suite in the same way. Signature are true suites, with kitchens as they’re designed for longer stays. Palazzo is one (very) large room, with a bathroom, bedroom area then you step down into the living room area. There is no fridge, coffee machine, microwave etc.

comparable MGM properties quality wise would be Aria, Bellagio or Delano.

I’m not sure what prices are like in August but the rate sounds decent considering that includes resort fee, taxes and a weekend.

I’ve only ever booked via IHG, but as long as they have your number on file it should be fine. You’re unlikely to get a great upgrade unless they’re full. I’ve stayed twice as spire, the first time we got upgraded to a larger room with wet bar and strip view from the standards room because they were full for a conference. It was brand new as had just been refurbished - we were also offered a terrace room but they were not yet refurbished. Last time we just got upgraded from a non strip view to strip view. It’s an IC property, so unless you’re IC Ambassador the upgrades can be hit and miss.