I just removed the baseboards in my room in order to put some closets flush against the wall. I noticed there is a gap under the wall and the floor/laminate and my instincts are telling me they need to be filled with caulk or something for insulation and pests. Is it necessary? If so, what should I use to fill the gap? I live on the bottom floor of a condo unit and there is concrete below the laminate.
To start with, that kind of a gap is common everywhere.
Regarding pests, your dwelling is more permeable than you'd ever think, so closing off this one thing isn't going to solve any problems. If they exist, pests need to be dealt with at their source (ie, nests), not at their symptoms (ie, them walking across your floor).
If you still want to seal, you need something flexible enough to not impair the expansion/contraction of your floor and not interfere with your baseboard. Nothing comes to mind.
Capsule summary: don't worry about this.