So I've been look to try and find whether Better critical will effect sneak attack damage or if it only effects VAT critical's so far tho the only info I've found relating to whether it does or doesn't has all been pre-release.

Anyone know?

It effects all criticals. Sneak attacks aren't considered critical hits, they're just sneak multipliers.

So for a sneak attack build I'm better off staying with ninja and mister sandman for damage multiples and ignoring luck?

I ignored luck 100% as a stealth build and I one-shot people on Survival difficulty.

You can ignore luck if you want but if you land a critical sneak attack? that's gonna be massive damage

but Bloody Mess is quite a nice perk

Felt it was kinda gimmicky after a while, lost immersion from playing as a sniper/ gunslinger when random explosion happen.

Probably go into luck way later in the game then, i rarely use vats so not as much of a priority compared to agility.

I'm level 50 which is the soft cap and I haven't touched it, lol. Never felt the need to put any points into luck. I went with raising endurance for the water-breathing perk.