I race both formula and raceboard, and as you have said they are quite a different experience, but both are great fun. In my opinion you have to more "committed" to get the best out of the formula kit -obviously these boards are designed to go upwind and downwind with large sails/large fins and this is where they perform the best and feel the best. Although you can sail them across the wind there are better boards that are more fun for this.
The raceboard is mostly slower than the formula board but has the ability to "slice" upwind on the rail - a great experience quite different than upwind on the formula board. It's hard to describe, but certainly a "softer" ride than the formula which can be quite "jarring" in choppy water. The raceboard is easier to "recreational sail" than the formula board - great to go exploring along the coast or around the lake and of course can still make ground if the wind drops off.
To get the best out of the raceboard, specific "raceboard sails" are the go,(they have a tighter leech than formula/freeride sails), however the raceboard is less sensitive to sail design (and size) compared to the formula board. A formula sail on a raceboard can work well but a raceboard sail on a formula board doesn't work very well. Basically any sail will work OK on a raceboard.
The MOD raceboard that you have is still a very good board, particularly when the wind is up. Modern raceboards tend to have a bit more volume, particularly in the back of the board - an advantage for racing in lighter winds and for heavier sailors.
I reckon formula board design has improved a lot more than raceboard design in the last 10 years - if you compare the latest formula boards to your SB 186 it is a bit like chalk and cheese (the latest ones are faster, feel better on the water, point higher etc) , however the latest raceboards (eg SB 377) compared your MOD is not such a large difference.
Although I haven't sailed the Exocet D2 I have seen it raced and I reckon it demands a high skill level in choppy water or ocean swell. Probably the same comment for the wally. I'm not sure about the Kona One.
I think there is a discussion about "recreational formula" setup somewhere else on this forum.
Have fun