I am trying to get rid of old type raspberries as I want to get the Purple Royalty type. They have larger berries.
I cut the canes down, and then when they form leaves near the ground , I spray them with WipeOut.
Caroline

If you want to kill your primocane raspberries, you can use any of the methods you proposed. The easiest would be to spray with glyphosphate (Roundup) when they are actively growing. May take 3 weeks for them to die, but they should die. Glyphosphate does not persist in the soil, so after the old canes are thoroughly dead you can use the space for whatever you want.