They also list the room types as studio, 1 bed, 2 bed, etc and 4800 points would go even further (2 bed) in RCI high season!
If you book through the HGVC portal, you will always trade on the point chart that you mentioned above. RCI points charts and TPUs don't affect us at all. Hilton has their own trading points system and it doesn't change. Even if you book a week before check in, the chart stays the same. You don't get a discount like every other system does.
DVC has become a difficult trade to get. You can put in a search for it 2 years in advance and hold your place in line. DVC won't make a deposit until about 6 months before the check in date. So, while you need to put in your request years ahead to get a place in line, you won't know if you get it until a few months before. Some people will make a Hilton reservation and wait it out and drop it if their exchange comes through. If you pay the $15. to become a Tug member, you'll have access to the sightings forum which has a thread about DVC deposits that you can watch.
If you want to use RCI to book a larger room in Hilton for less points than using Hilton alone, it can be done, but usually only if someone cancels a reservation. As Hilton owners, we are blocked from seeing any RCI inventory that is further than 9 months out. Hilton does their bulk deposits 12 - 18 month ahead of time. By the time we get to the 9 month window where we can see, everything is already taken. People do cancel stuff though, so if you have an ongoing search set up, you may get it.