For paddles there are a LOT of variables.
Greenland (straight and narrow,) Scoop (the most common,) Canoe paddles, hand paddles, Scooped Greenland..., etc.
Longer usually means flatter water with faster high end speeds. Shorter means lots of leverage, fast movement, easily flipped side to side, best in whitewater but, blade shapes can change.
Materials: Wood, the traditional. Plastics(often injection moulded,) Composite injection moulded (plastic with fiber reinforcements,) Fiberglass, Carbon, etc. I prefer Carbon but it only saves a few ounces over fiberglass. Fiberglass is more forgiving. Plastics can be good or bad depending...
Metal, wood, carbon, fiberglass, etc... Then you get into bent shafts, feathering, and all that. Ignore it. Choose what is comfortable. But, I would recommend you get used to a moderate feather.
Anyway, the one REI is offering is a good cheaper model. It is HEAVY at 2#6.4. The length can probably be cut down with a grinding wheel if needed, but it is fairly short to start with. It might be a bit long for a packraft, though. It IS a good deal for a usable paddle.
Packrafts can use hand paddles. Think of snow shoes mounted to your hands. They work, but are not real great in whitewater.
PFD's all very. The higher the weight carried by them, the straighter in the water you will be. Currents can change this easily. I use a 15# PFD or about 1/12-1/13 of my body weight. More than enough for me because I don't get excited when my head is near the water line. Some people like more. 1/4-1/5 is about the usable limit. 50# is a LOT of PFD. But, I use a 20# PFD for my 3.5 year old grandson. He can swim, but, not too well...I do not want him to get panicky. And, I make sure the bouyancy is on his chest, not his back. He will float head facing up, not down as with many. This is close to 1:2 for his weight(41 pounds.) It kind'a depends.
The pics you mention are mostly kayak PFDs. These leave you struggling to swim because of the angle the support you at. But, they need that to avoid bunching up with the cockpit. A trade off.