iirc there is a 28mhz line from denise? that is halved to provide a 14mhz clock to a 16mhz 68000.
there is some incompatibility with the floppy especially but some programs have problems as well.
some polygon type programs speed up a little, as well as some cpu bound programs but other than that its not worth it. lha would speed up some.
there was a mod that synced the clocks so a switch could flip between 7.16 and 14 I don't know haw well it did though. Without it flipping frequencies would freeze the machine.
The 68000 has a lot of "dead" time on the bus, time where it's not doing anything, during multiplies or any other long instruction. This would reduce that, the memory would keep up as well as with any '020 or '030 accelerator