Here are my general thoughts on your questions.

(1) how nice the actual room accommodation may be
Canyon Suites will be the nicest, then the main hotel, and lastly the residences. Not to say the residences aren't nice, they just feel a little dated. The Canyon Suites and regular hotel both had substantial renovations in the last year or so though, so not surprising.
(2) how effective the air con may be
I can't promise you they will hit the low 60s, but we've never had any issues during the summer and we keep the air around 67-68.
(3) how luxurious the experience may be
The property is great, but it is a huge resort so the service won't blow you away. I've experienced long lines for check-ins, 30-45 minutes waits for breakfast seating, full restaurants for dinner reservations, 1-hour plus room service delivery, slow pool service, completely full chairs at the main pool, etc. These only happen occasionally and with one exception, we've always had very enjoyable stays. But when I think of true luxury, none of those things should ever happen.

So if service is something you place a lot of value on, I would suggest the Canyon Suites. The Canyon Suites has its own pool, where I've never had issues getting chairs or fast service even on holiday weekends. It also has it's own bar/restaurant where they serve breakfast and evening snacks. The regular resort restaurants are great, but it's nice to have another option. Note that the residences do not have access to the Canyon Suite amenities. They also supposedly give Canyon Suite guests priority access to golf, restaurants and spa, but I'm not sure how useful it is. I've only tried to use it once, and they weren't able to get us same-day reservations at the hotel restaurant on a sold-out evening.

I would say the regular resort is a slight notch above a Westin/JW Marriott resort, and the Canyon Suites is more akin to a domestic Ritz Carlton resort.

(4) if there are any differences in service or food/beverage
As noted above, the Canyon Suites gets you access to the Canyon Suites pool complex and restaurant and the Canyon Lounge. Otherwise no, all rooms have access to the main resort facilities, restaurants, room service, etc.
(5) if a Residence is truly nicer than a regular room/suite in the other properties
It's nicer in that it's much larger and has a private hot tub or pool. But finish wise, the other rooms are "nicer".

If I'm with my kids, I'll take the residences with the kitchen, pool, extra space, etc., but if it's just me and the mrs., I would choose the Canyon Suites instead, especially if you can get a pre-upgrade or have an SNA clear. The points room being limited to the 2nd floor unit also lessens the appeal of the residences since that's the worst residence unit and a small hot tub isn't nearly as useful as a private heated pool (not sure why they call it a plunge pool because it's actually a pretty good size) and hot tub. We were told that the residence bookings book into specific residences and that they don't do upgrades within those, but it may be worth calling to see if you can pay a little extra cash to be moved to one of the ground floor units well in advance of your stay.