Speed on paid search is simple to reason about: you paid for a visitor who is already slightly impatient, and every second of white screen is a chance for them to go back to the results and click a competitor you are also bidding against. Test on a real phone, not a narrowed desktop browser. Cut the hero video, lazy-load anything below the fold, and make sure the first screen paints before the fonts and the tag manager finish.
On mobile, the question is whether the first screen shows the promise and the action. A logo, a hamburger menu, a cookie banner and a stock photo is a first screen that shows nothing. If the ad offered a phone call, the number should be a tap target at the top. If it offered a quote, the first field should be reachable with one thumb.
The form is where most paid search pages lose their last visitors. Ask for the minimum the next step needs. A quote request does not need a company size, a job title and a phone number if a sales rep will ask those on the call anyway. If you need qualification, ask one question and keep the rest for later. Label the button with the outcome, say what happens next, and confirm on a distinct thank-you state so your tracking and your visitor both know it worked.