As
@123 said, tariffs are more or less an exclusive function of the executive branch, so it's one of the easiest things an incoming Trump administration can do. The numbers being thrown around are: up to 60% on Chinese goods (there are currently still 25% duties on a significant amount of Chinese imports from the first administration), 25% duties on imports from Mexico, and a flat 10% on all imports regardless of Origin.
I work in an outdoor sports industry where all manufacturing is overseas with a significant amount in China. A lot of companies did attempt to diversify their supply chain when the first Chinese duties were announced, but almost none of it was onshored back in America; Most of it was moved to other Asian countries and even then a significant portion remained in China. All of that cost is passed along to your local shops and eventually to the consumer via raised prices.
As far as the exemptions are concerned, there were a lot of trade organizations and dedicated civil servants who worked on passing exemptions on items that may no longer have the support of the administration so I don't think it can be counted on. Also, a lot of the exemptions were retroactive, which means the companies importing already paid the duties, raised the cost of the goods and sold them into the market before the exemptions were approved. That money does not just get refunded to the importer, you have to work with a dedicated duty drawback professional at significant cost to try and recover those paid duties. Most companies don't have the time or money to do so, so it's functionally immaterial.