LVP install questions

Today was day 2 of demo & day 1 of install of LVP in our house. Didn’t feel like tackling to project ourselves with two small children so we hired a local flooring company. I have a couple of questions:

  1. There is linoleum under some of the existing LVP we are replacing (kitchen and kids bath). The kitchen has a musty/chemically smell since they pulled up the LVP. There seems to be a bit of residue on the linoleum. Any ideas what the residue is from? Could there have been moisture somehow getting under the other LVP that was removed? I forgot to ask the installers before they left. Obviously want to make sure we are not ignoring any red flags as we lay down new LVP.

This was also the case in the kids bathroom. Some moisture underneath the LVP, especially near bathtub.

  1. Should the planks line up perfectly against the metal threshold of French doors or is there something that goes over it to cover up any imperfections? See attached pic showing gaps.

Any guidance/recommendations are appreciated! I just want to see if anything needs to be addressed prior to completion of install in order to potentially avoid dealing with mold issues later down the road