Luddite that I am, I don't have, have never used or even touched, or even thought about getting an SB-27 so can't comment on it.
Slaves? I've revisited B&H's site, looked harder. The Wein Peanut, Hama and Keiser cubes, Vivitar SL-2, Wein hot shoe, are logically equivalent. The big difference between the Peanut and the hotshoe types is that since the Peanut plugs into the flash's PC cord socket, with it one has to find a way of attaching the flash to the bracketry. Which is why I use hot shoe types with holes in the base threaded 1/4" x 20.
All of these slaves are pretty sensitive. I don't see what you mean by "behind the actual flashes." FWIW, all of my slave triggers face the subject, are triggered by light reflected from it.
While looking around on the B&H site I came across the Morris Midi Slave DC. A little powerful for closeup if the specs are to be believed, but that's what ND (NOT COLORED) gels are for.
Two ways to reduce illumination on the subject when fixed-output flashes are used. ND gel(s) on the flash, increase flash-to-subject distance. Get a Rosco swatchbook (the little one) from B&H. $0.01 plus postage.
In my rigs -- I've made and used 3-flash rigs too -- one flash is fired by cable, the other(s) by slave triggers. Y-cables are bad luck. More connections not to work and always the risk of polarity problems.
You really have to step out of the 35 mm auto-everything mindset. For closeup with flash that mindset adds needless complexity and ways of going wrong.
To encourage you, these days I travel with a little 2 flash rig for my 105 MicroNikkor, another for my 2x3 Graphics, a Vivitar 283 with VP-1 for the Graphics, and a big mutha' SCA 300 flash with module etc. for my 8008S. The little 2 flash rig for the Graphics replaces the 2x283 + VP-1 rig I used to use with them.