Sydney Country Pine 7 in. W x 48 in. L Resilient Vinyl Plank Flooring (18.91 sq. ft./case)

It's personal choice. We used neither on our dry concrete mudroom floor. If it were below ground, I'd lay a vapor barrier so it can run up the side walls, but not needed above ground since this floor provides a self-sealing field. I pulled the following from the installation PDF that's available to you too on the item's webpage: Additional layer of 6 mil poly film or equal vapor barrier with a perm rating of 1 or less may be used as an additional layer of protection. Installation of 6 mil poly film underlayment is recommended for floating method only in high moisture applications. A second underlayment is allowed under any currently sold SPC Product with attached underlayment in a residential application. If installed over a second underlayment, this underlayment cannot be greater than 3 mm thick. IIC (ASTM E492-09) and STC (ASTM E90-09) lab testing on certain SPC products tested with and without a second layer of underlayment, to date, does not indicate that a second underlayment will provide additional acoustic benefit.

No, you do not!

Here is a close up next to red oak hardwood flooring. It's more of a rustic brown.

It is 5.5 mm with a 20mil wear layer

Yes, when installed correctly (clicked together tightly), it self-seals between planks as it has adhesive on the flanges. It's a floating floor and you need to leave a small gap around the perimeter of the room to allow for expansion and contraction. There are mixed opinions on sealing the perimeter in a bathroom so the floor is fully waterproofed in case of tub/sink overflows. Each bathroom is different so you need to evaluate yours. Sealing is done with caulk so the gaps can remain flexible. There are a few ways to seal it too, so I'll leave it to you to decide, but here are some options: a) Simply caulk the gap b) Put quarter-round (with or without baseboard) molding (PVC would be best for bathroom, not wood) over the gap against the wall and caulk the top and bottom edges of the quarter round. That will also create a seal. The caulk will hold the trim in place, no need to nail into your tile or anything. c) You can do a mix of both above options because quarter round can't be put against curved surfaces like toilets and some tubs, so e.g. trim the walls and just caulk the fixtures. Silicone chalk is better than latex for this purpose but more difficult to install and not paintable, so choose accordingly. Both types will work.

Perhaps not under the same exact names as the flooring but I think you can find trims that blend well enough. Here are all the Shaw trim products: https://www.homedepot.com/b/Flooring-Vinyl-Flooring-Resilient-Flooring-Vinyl-Trim/Shaw/N-5yc1vZc4inZ1d2?mtc=SEM-B-F_D23-G-D23-23_4_VINYL_FLOORING-Multi-NA-NA-ETA-NA-NA-NA_DSA&cm_mmc=SEM-B-F_D23-G-D23-23_4_VINYL_FLOORING-Multi-NA-NA-ETA-NA-NA-NA_DSA-71700000032321073-58700003835937302-39700030691396526&gclid=Cj0KCQjwvb75BRD1ARIsAP6LcquQ3rKnNiJOCRgUO_DuhLDAtBH0GigYgXTxeWE2dH-NWXZlX39KnQwaAiR9EALw_wcB&gclsrc=aw.ds

no

Yes, The Home Depot sells samples of them online.

Rob, i have not found that they do.. usually you can find what you need from the selection offered at the store. in my case i went with white since it matched my baseboards & worked as an accent under my cabinets.

Yes, The Home Depot sells samples of it online too.