Unless you have a specific reason to use some other mode, I would use the combined mode.  It is the most flexible.

That's just not going to work.  In fact, the "fabricpath topology 0" command isn't going to do anything.  All vlans are in topology 0 by default. And all fabricpath links always carry topology 0.  Fabricpath is designed to automatically load balance ...

The F2e cards can only support 16K MAC addresses per SoC (Switch on a Chip) and a total of 16K ARP entries total.  The command "show hardware capacity forwarding" will show you the complete picture for layer 2.   That's why we now have 7706s with F3 ...

The 6000 has L3 built in.  No daughter card is available nor is one needed.