Wub-cada's a nasty little monster. Those 5 MPL, with an XL300 and crammed with DHS, do a lot of work. It only seems lackluster on paper because MPLs are already meta-riffic, and don't require a lot in the way of quirks to make them even more popular.
I've seen people preaching the gospel of a 1LPL+3ML on the X5, claiming the build actually does some work because of the way the quirks line up (especially the range). I levelled mine with 4ML and Streaks last summer. I enjoyed it
Don't be afraid of the midsize engine. They're more tonnage efficient, and allow for gunzy loadouts like the previously-mentioned 3LL build on the 3M.
That said, I admit to running the 3C troll build above with the MGs and ERPPC. There's supposed to be a build that includes the ERPPC and an AC5 out there. I may yet try it
For your 3rd choice: 2A is steady, X5 has hero bonus (and energy range and option for missiles), 3C for lulz, 2B for wubz.
If I had to pick one with an autocannon held to my head, I'd say this: Wub-cada is best-cada.