Does it matter what type lug I use or how its crimped if using a crimp type lug?. or is a allen head type lug OK? With or with out the ridgies that hold the wire tighter that some type have.. thank you... aluminum... 4/O

Any lug,either compression or mechanical is fine, just needs to be rated for aluminum wire. A compression lug for #4/0 will require a hand or hydraulic crimping tool with the specific die to fit the crimp lug.

A mechanical lug only needs nuts ,bolts, and lock washers, and a allen wrench.

Be sure to treat the bare stripped wire with wire brush, applying anti-oxidant compound, and properly torque the connection.