Is the 150 reef ready? (overflows, drilled, etc)
The only advantage of LR is it contributes to bio filtration but is NOT a single source for it in most cases. That and it looks good...
For any FO/FOWLR you really need a protein skimmer. Whether you run one larger unit or two smaller ones as long as the bioload is kept up with you are fine.
As for the wet/dry's, you can look and see what the recommended gallonage of bio balls are for 150 gallons but I seem to recall about 3-4 gallons will do it for most stocking levels. Again, if you get that from one larger filter or two smaller ones isn't important. (maybe a bit of extra plumbing effort)
Also keep in mind that water changes are always an option/necessity. Just keep an eye on water parameters and when you see them start to slip do the change. Soon you'll figure out what water change schedule is par for your bioload.
Hope this helps...