I haven’t played with Aalto much but I really enjoy Kaivo. Looks like the waveguide/delay module is just a super fast delay line with a peaking filter?
I almost got a CG Products delay before I decided to go for a d0 instead, and I use it in a similar fashion to the Aalto module sometimes. The 1022 sounds lovely but the shortest delay possible is around 1.3 ms which in pitch terms falls around F1. d0 is an interpolating delay (capable of delay times smaller than its sample-rate) like the one in Aalto and goes down to 2 micro seconds which equates to around a D#8, so a much wider range. I tend to use mine for physical modeling, but I’ll run oscillators through it and use it as a phaser or comb filter or just an indescribable tone shaper as well. There’s so much you can do with a super-short delay in a modular system.
The Doepfer BBD’s are really noisy, also needing external filters, but they seem to always have a lofi edge to my ears, even when filtered, which is great if you’re into that sound.