If you are planning on debugging your software then I recommend SASC since it has the best source level debugger by far.
If you are just going to code bug-ridden nonsense then you can just use anything, even cross-compile. Protip1: don't cross-compile. Protip2: Using WinUAE is not cross-compiling.
As for Asm, the Amiga has many good assemblers: Devpac, Asm-One, Barfly, PhxAss and probably others I forgot about.
All the Amiga's dev software is tiny. So just install everything.
Trying to interface asm to any GCC-derived compiler is going to drive you insane and raise your bloodpressure. You could die of a stroke. We don't want that. So I recommend any normal C compiler that cooperates with asm, such as SASC for sure. But I think VBCC and DICE cooperate in a friendly manner too (I just can't remember for sure).
I have used a few different Amiga C compilers + read the instruction manuals to a few others. I have used at least 4 different assemblers.