Lapras - WG/ HP - thought Ice was best?

Yah, double Ice moves is best for Lapras. It is a water mon, so dual water moves will get you STAB but Vape still better alternative to power up as candies more easily available.. I don't think the WG/HP is that much better because I consider Lapras my ice specialist. I would power up you Lapras as an ice attacker only

Both water movesets and ice movesets have 'A' grades. Depends on what your using it for.

Because Lapras is like a less strong Vaporeon in terms of wg/hp, that is is high rated moveset, you will hit hard rhydon but he will hit you hard too because rock stabs ice

However if you want a lapras try to catch one with double ice moveset, because for water vaporeon is far better

It would be a good generalist; but the only thing it does better than vaporeon is resist ice. With eevee candies much easier to come by, it isn't worth powering (unless there are a lot of ice Mon around you).

I am curious why water gun hydro pump is now the highest rated attack set for Lapras.

Actually, it's tied for highest rated. There are six A-rated Lapras attack movesets, and they are not listed in rank order. As GamePress makes clear, all A-rated movesets are considered essentially equal and optimal for that particular mon.