Regarding the link you supplied, They don't say what they are using but the process I have used is
is basically the same. Using a roll type press the fujiflex print is laminated to the dibond with an adhesive layer.
Then an optically clear UV protective layer is laminated on top of the print, encapsulating the print between the
UV layer and the dibond. The problem is, the UV laminate or acrylic layer people are using for this
scratches way too easy to be practical for my method of sales. The print is safe, the surface is not and you can't
remove the surface laminate without destroying the print. If you have the right tools and knowledge you may be
able to buff out minor scratches in acrylic, doubtful on the thinner UV laminates.
Dealing with labs, I never allow them to convert or adjust anything color related. I tell them to print it exactly like I sent it.
I order small proofs and make all adjustments to color ect.. on my end until I am happy with the result. When you find a good lab
you will usually be good to go with the first proof as long as you are properly calibrated on your end. If your lab refuses to not monkey with your files, you need to find another lab.
If they require Adobe RGB or sRGB then I convert and make adjustments on my end. I agree with Brian that there aren't many ,if any, printers out there that can print more
than sRGB so I believe you have another issue going on.
Regarding resolution, for best quality I res my files up to the native resolution of the printer they will be printed on using the guidelines mentioned on this forum by Jeff Schewe.
Only used Bay Photo for metal once a couple years ago. Their color was good but stopped using them for other reasons.
No experience with Imagewizards.