I've read conflicting information.
1) Do preludes spread under ground by root?
2) Do preludes spread by tip rooting?
My preludes have spread from underground roots. Fairly aggressively (like most raspberries). I have not seen any tip rooting.
In general only black and purple raspberries tip root. Prelude though is a strange one. It is Summer bearing yet I guess can produce a fall crop!? I suppose any would tip root, if you could force the cain on the ground. I'm not sure how you would do this though, as many reds have somewhat sturdy hard cains. They need support because of crop load, although some do not. Anyway this one suckers a lot according to Indiana Berry Co, and I trust that site, they know their berries!
I heard it is excellent cultivar. Mine was just planted this year. I'm experimenting with many cultivars to see what works for me, and what I like best.
My Preludes didn't tip root. Its a good berry, I found it similar to Caroline.